CN102097934A - Hysteresis mode buck DC/DC (direct current/direct current) switch converter - Google Patents

Abstract

The invention provides a hysteresis buck DC/DC (direct current/direct current) switch converter, comprising an input voltage source, an output filtering inductor and an output filtering capacitor, a main switch, a synchronous switch, a hysteresis comparator and a dead time control and driver module, wherein the output filtering inductor and the output filtering capacitor are connected in parallel; the switch converter is further provided with a hysteresis window control module; an input voltage and an output voltage are both input in the hysteresis window control module; an upper sideband voltage and a lower sideband voltage which are generated by the hysteresis window control module are respectively input to the positive input end of the hysteresis comparator; the output voltage of the switch converter is input to the negative input end of the hysteresis comparator via a coupling resistor; the main switch is connected with a branch resistor; the branch resistor is connected with a branch capacitor in series; the branch resistor is connected with the coupling resistor; and the branch capacitor is grounded. The switch converter provided by the invention can adaptively adjust the size of a hysteresis window and stabilize the switch frequency according to the input voltage so as to achieve the advantages of simple structure, fast response and the like of the hysteresis mode, remove the influence of the input voltage to the switch frequency, and realize quasi-frequency control.

Description

Sluggish pattern voltage-dropping type DC/DC switch converters

Technical field

The present invention relates to a kind of sluggish pattern voltage-dropping type DC/DC switch converters.

Technical background

Power supply is the device that power is provided to electronic equipment.Whether the size of power, voltage and current are stablized, and all will directly have influence on the service behaviour and the useful life of electronic equipment.In modern portable electronic system, as mobile phone, digital camera/video camera and notebook computer etc., no matter be to adopt the batteries power supply, still by electric main (perhaps through AC adapter) power supply after rectification, all can there be bigger variation in supply voltage.Therefore, the input power supply generally can not directly be powered to electronic system, and must pass through stabilized voltage power supply earlier so that provide continual and steady energy to electronic system.A high-quality stabilized voltage power supply can provide good power output in wide in range input supply voltage scope.And along with information science and development of integrated circuits, market is constantly increasing for little power consumption, demand energy-saving, the intelligent electronic product.This has proposed new challenge to the power management IC that research and development has high-performance and high power supply quality.

At present, Chang Yong DC/DC stabilized voltage power supply mainly contains three major types: linear stabilized power supply, capacitance-type switch power supply and inductance type Switching Power Supply.Linear stabilized power supply as LDO, though output ripple is little, always has certain pressure drop owing to adjust on the pipe, and power consumption is bigger, and conversion efficiency is very low; The capacitance-type switch power supply is commonly called as charge pump (Charge Pump), and in order to change the power topology, inside needs the integrated switch array and increases area of chip and power consumption, reduces conversion efficiency; The inductance type Switching Power Supply is called for short " Switching Power Supply ", by the recently stable output of the duty of power controlling switch.Different with linear stabilized power supply, the adjustment pipe of Switching Power Supply just is operated on off state, thereby the loss that is caused by switch is very little, and conversion efficiency is very high, can reach more than 90%, and big load current can be provided.List says that from conversion efficiency Switching Power Supply is the highest in three kinds of DC/DC stabilized voltage power supplys.High conversion efficiency helps energy-conserving and environment-protective, and for battery-powered portable type electronic product, high conversion efficiency also helps to improve the utilance of battery.

The BUCK converter is a kind of DC/DC Switching Power Supply that high input voltage can be converted to low output voltage, and the concrete structure of sluggish pattern control comprises input voltage source as shown in Figure 1, filter circuit and with the filter circuit load in parallel; Described filter circuit comprises inductance and the electric capacity that is connected in parallel, and is provided with main switch between inductance and the input voltage source, is provided with synchro switch between inductance and the ground; The output of filter circuit is connected with the negative input end of hysteresis comparator, the positive input terminal input voltage signal of hysteresis comparator, the output of hysteresis comparator with can produce the non-intersect switching drive signal that changes, avoid the Dead Time control and the driver module of the conducting simultaneously of main switch and synchro switch to be connected; Described main switch and synchro switch are controlled by Dead Time control and driver module.

In this typical control structure, system is by remaining on output voltage ripple by output reference voltage V _RFERealize adjusting in the retarding window of setting with sluggish PWM comparison circuit to output voltage.The crucial control waveform of system works when the CCM pattern as shown in Figure 2.As main switch S _HConducting, lock-in tube S _LDuring shutoff, output voltage rises, until rising to sluggish upper sideband V _{HYS_H}The time, main switch S _HTurn-off lock-in tube S _LConducting descends output voltage; When output voltage drops to sluggish lower sideband V _{HYS_L}The time, main switch S _HAgain conducting, lock-in tube S _LAgain turn-off the switch periods that beginning is next new.For fear of the job insecurity that is caused by LC phase shift problem, system need guarantee at the input of sluggish PWM comparison circuit the enough big output voltage ripple consistent with switch phase arranged.In actual applications, also need to use the relatively large electrochemical capacitor of equivalent series resistance (ESR) or at non-essential resistance (R of output capacitance branch road series connection _C).This not only can increase design cost, also can cause certain power consumption and reduces conversion efficiency.

Because typical sluggish pattern control is directly to guarantee system's operate as normal by the control output voltage ripple, therefore, its switching frequency depends critically upon system parameters.

The main control model of BUCK converter comprises voltage mode, current-mode and sluggish pattern.For voltage mode and current-mode, in order to ensure working stability, the both need carry out complicated feedback control loop compensation.This has not only increased design difficulty, has also increased product cost.In addition, owing to the restriction of switching frequency to loop gain bandwidth, both transient responses are also relatively slow.Sluggish pattern is considered to that control structure is the simplest, transient response control method the most fast.It need not the design compensation network, and can make response to the load current saltus step in the same switch periods, is well suited for being applied in microprocessor, digital signal processor and the some other dynamic load with high Slew Rate.But switching frequency seriously is subjected to influence on system parameters, particularly input voltage.The bigger variation of switching frequency will cause potential electromagnetic interference (EMI) problem, makes sluggish pattern be not suitable for being applied to some EMI is required relatively stricter occasion.

In order to solve the problem of switching frequency fluctuation in traditional sluggish pattern, particularly the input voltage variation can come the stable switch frequency by designing a negative feedback control loop usually to the influence of switching frequency.Common control method has: (1) utilizes frequency/voltage (F/V) change-over circuit to convert switching frequency to corresponding with it voltage, and it is remained in output reference voltage, comes the stable switch frequency by the size of regulating retarding window; (2) utilize phase-locked loop (PLL) modulation technique, come the stable switch frequency by the conducting/turn-off delay time that changes the system power switch; (3) utilize phase-locked loop (PLL) modulation technique, realize the stable of switching frequency by the size of regulating retarding window; (4) (Constant On Time, COT) control technology obtain relative constant switching frequency by the constant that the ON time with system's main switch is made as with input voltage is inversely proportional to utilize constant ON time.Wherein, first three is planted control method or needs error amplifier, or needs extra clock signal, the design more complicated of control loop.Though the COT control technology need not to use error amplifier and extra clock signal, but owing to have only a sluggish lower sideband, it can only make quick response to saltus step on the load current, then will be subjected to the restriction of system's main switch ON time to the response of saltus step under the load current.Slope pulse modulation (Ramp Pulse Modulation, RPM) structure is the modified model that combines the COT control of modulation of output voltage DC level and fast dynamic response function, be used as determining the threshold voltage of main switch ON time by the output reference voltage in the error signal replacement COT control after error amplifier amplifies with output voltage and output reference voltage, thereby in modulator output voltage DC level value accurately, the ON time that makes system's main switch reduces to reduce the overshoot of output voltage during saltus step under load current adaptively, and the quickening system is to the response of saltus step under the load current.But the RPM structure has increased the complexity of design owing to used error amplifier with regard to the necessary compensating network of need design.

Summary of the invention

For overcoming the above-mentioned shortcoming of prior art, the invention provides and a kind ofly can regulate the size of retarding window with the stable switch frequency according to input voltage adapting ground, thereby in advantages such as the simple and quick response of the sluggish mode configuration of maintenance, eliminate the influence of input voltage, realize the sluggish pattern voltage-dropping type DC/DC switch converters of control certainly frequently switching frequency.

Sluggish pattern voltage-dropping type DC/DC switch converters, comprise input voltage source, output inductor that is connected in parallel and output filter capacitor, be arranged at the main switch between output inductor and the input voltage source, be arranged at the synchro switch between output inductor and the ground, hysteresis comparator and can produce the non-intersect switching drive signal that changes, avoid the Dead Time of main switch and synchro switch while conducting to control and driver module;

It is characterized in that: also have in the described switch converters and can produce retarding window control module (the Adaptive Hysteresis Window Control of a retarding window according to input voltage adapting ground with the stable switch frequency, AHWC), input voltage and output reference voltage are all imported in the described retarding window control module, and upper sideband voltage and lower sideband voltage that described retarding window control module produces are imported respectively in the positive input terminal of hysteresis comparator;

The output voltage of switch transformer is imported in the negative input end of described hysteresis comparator by coupling resistance, one end of the close output filter capacitor of described main switch is connected with branch road resistance, described branch road resistance and branch road capacitances in series, one end of the close branch road electric capacity of described branch road resistance is connected with an end of the close described hysteresis comparator of described coupling resistance, described branch road capacity earth.

Further, described retarding window control module comprises retarding window generation unit settling time and retarding window sideband generation unit;

Described retarding window generation unit settling time comprises the amplifier of the threshold voltage that the difference of obtaining input voltage and output reference voltage and output are proportional to described difference, comparator and first internal current source of negative input end voltage is provided for comparator; The threshold voltage of described amplifier output is as the positive input terminal voltage of described comparator;

Described first internal current source is made of first unity gain amplifier and first current mirror, and described internal current source and first internal capacitance and the adjusting resistance that can regulate the actual output accuracy of retarding window settling time are connected; One end of close described first current mirror of described adjusting resistance is connected with the negative input end of described comparator;

When threshold voltage during greater than negative input end voltage, described comparator output high level; When threshold voltage during less than negative input end voltage, described comparator output low level;

Described retarding window sideband generation unit comprises second internal current source and first switch that is connected in series, upper sideband electric capacity, lower sideband electric capacity and second switch; Described upper sideband electric capacity and the 3rd switch in parallel; Described lower sideband electric capacity and the 4th switch in parallel, described first switch and second switch are controlled by retarding window settling time, voltage between first switch and the upper sideband electric capacity is upper sideband voltage, and the voltage between second switch and the lower sideband electric capacity is lower sideband voltage;

Described second internal current source is made of two current mirrors and a unity gain amplifier.

Further, the internal capacitance of described retarding window generation module settling time is in parallel with capacitance switch.

Further, described input voltage source is in parallel with the input voltage filter capacitor, described input voltage filter capacitor ground connection.

Self adaptation retarding window control (Adaptive Hysteresis Window Control, AHWC) technology is by self adaptation retarding window control circuit, make sluggish Mode B UCK converter according to input voltage, according to certain principle, the upper sideband voltage of adaptively modifying retarding window and lower sideband voltage promptly change the size of retarding window, to keep the relatively stable of switching frequency, avoided realizing control certainly frequently owing to input voltage changes the switching frequency fluctuation problem that causes.And, by designing sluggish sideband periodic refresh mechanism the upper sideband voltage and the lower sideband voltage of retarding window is periodically refreshed when each switch periods begins, thereby eliminated the influence that input voltage changes and the Leakage Current of internal switch causes retarding window.The size of retarding window is corresponding one by one with the size of input voltage.When input voltage increased, retarding window can the corresponding increase according to certain principle, and when input voltage reduced, retarding window then reduced according to same principle is corresponding, and switching frequency is stabilized on the analog value.Choose and be provided with by suitable system parameters, adopt the switching frequency of the sluggish Mode B UCK type switch converters of the AHWC control technology of inventing just can be set in advance in analog value, and have controlled function certainly frequently.

For voltage mode control and Controlled in Current Mode and Based, sluggish pattern is considered to the simplest and the most a kind of control method of transient response of system configuration.The AHWC control technology is with respect to the more existing control method that solves switching frequency stability problem in the sluggish pattern, its advantage mainly comprises: (1) AHWC control technology just can make retarding window according to the corresponding adjusting of making of input voltage adapting by simple control circuit, eliminate the fluctuation problem of switching frequency, realized control certainly frequently.(2) the AHWC control technology accurately the DC level value of control output voltage equal the output reference voltage value of system, thereby do not have output voltage DC level error, i.e. the inaccurate problem of output voltage precision.(3) the AHWC control technology need not to use error amplifier and extra clock signal, need not to design complicated feedback compensation network, has kept traditional sluggish pattern control structure characteristic of simple, and the design of control loop is simple relatively.(4) the AHWC control technology is owing to kept two sluggish sidebands, the output voltage fluctuation that causes for load current saltus step and input voltage saltus step, all can make output voltage come back to stable state rapidly, avoid bigger output overshoot and stabilization time, kept the characteristics of traditional sluggish pattern fast transient response.

Description of drawings

Fig. 1 is the schematic diagram of typical sluggish pattern control structure BUCK converter.

Fig. 2 is typical sluggish pattern control BUCK converter key waveforms.

Fig. 3 is a schematic diagram of the present invention.

Fig. 4 is the schematic diagram of retarding window generation unit settling time.

Fig. 5 is the schematic diagram of retarding window sideband generation unit.

Fig. 6 is the key waveforms of AHWC control.

Embodiment

With reference to accompanying drawing, further specify the present invention:

Sluggish pattern voltage-dropping type DC/DC switch converters, comprise input voltage source, output inductor that is connected in parallel and output filter capacitor, be arranged at the main switch between output inductor and the input voltage source, be arranged at the synchro switch between output inductor and the ground, hysteresis comparator and can produce the non-intersect switching drive signal that changes, avoid the Dead Time of main switch and synchro switch while conducting to control and driver module;

Also have in the described switch converters and can produce retarding window control module (the Adaptive HysteresisWindow Control of a retarding window according to input voltage adapting ground with the stable switch frequency, AHWC), input voltage and output reference voltage are all imported in the described retarding window control module, and upper sideband voltage and lower sideband voltage that described retarding window control module produces are imported respectively in the positive input terminal of hysteresis comparator;

The output voltage of switch transformer is imported in the negative input end of described hysteresis comparator by coupling resistance, one end of the close output filter capacitor of described main switch is connected with branch road resistance, described branch road resistance and branch road capacitances in series, one end of the close branch road electric capacity of described branch road resistance is connected with an end of the close described hysteresis comparator of described coupling resistance, described branch road capacity earth.

Described retarding window control module comprises retarding window generation unit settling time and retarding window sideband generation unit;

Described retarding window generation unit settling time comprises the amplifier of the threshold voltage that the difference of obtaining input voltage and output reference voltage and output are proportional to described difference, comparator and first internal current source of negative input end voltage is provided for comparator; The threshold voltage of described amplifier output is as the positive input terminal voltage of described comparator;

Described first internal current source is made of first unity gain amplifier and first current mirror, and described internal current source and first internal capacitance and the adjusting resistance that can regulate the actual output accuracy of retarding window settling time are connected; One end of close described first current mirror of described adjusting resistance is connected with the negative input end of described comparator;

When threshold voltage during greater than negative input end voltage, described comparator output high level; When threshold voltage during less than negative input end voltage, described comparator output low level;

Described retarding window sideband generation unit comprises second internal current source and first switch that is connected in series, upper sideband electric capacity, lower sideband electric capacity and second switch; Described upper sideband electric capacity and the 3rd switch in parallel; Described lower sideband electric capacity and the 4th switch in parallel, described first switch and second switch are controlled by retarding window settling time, voltage between first switch and the upper sideband electric capacity is upper sideband voltage, and the voltage between second switch and the lower sideband electric capacity is lower sideband voltage;

Described second internal current source is made of two current mirrors and a unity gain amplifier.

The internal capacitance of described retarding window generation module settling time is in parallel with capacitance switch.

Described input voltage source is in parallel with the input voltage filter capacitor, described input voltage filter capacitor ground connection.

Fig. 3 is the control of self adaptation retarding window (Adaptive HysteresisWindow Control, sluggish Mode B UCK converter circuit topology AHWC), the output voltage V that adopts invention _OUTEqual output reference voltage V _REFV _INBe input voltage source, C _INBe the filter capacitor of input voltage, L and C _OUTBe the output inductor and the output filter capacitor of BUCK unit.AHWC control circuit in the frame of broken lines is used for producing can be according to the upper sideband voltage V of the retarding window of input voltage adapting conversion _{HYS_H}With lower sideband voltage V _{HYS_L}, promptly producing one can be according to the retarding window Δ V of input voltage adapting conversion _HYSDead Time control and driving (Dead Time Control﹠amp; Gate Driver) module is used for to two power switch S _HAnd S _LProduce two non-intersect switching drive signals that change, avoid the conducting simultaneously of two power switchs.

Output voltage V _OUTBy coupling resistance R _D, make the DC level value of output voltage equal output reference voltage V _REFPass through R _Add-C _AddCurrent i on the branch road _AddGive C _AddPeriodically discharge and recharge, make converter produce an extra ramp voltage at the negative input end of hysteresis comparator (Hys.Comp).Feedback voltage V _FBBe the DC level of output voltage and the superposed signal of extra ramp voltage.Converter passes through this feedback signal V _FBRemain on by output reference voltage V _RFERealize adjusting in the retarding window of setting with hysteresis comparator to output voltage.Work as C _AddOn voltage rise to sluggish upper sideband V _{HYS_H}The time, S _HTurn-off S _LConducting makes C _AddOn voltage V _FBDescend; Work as C _AddOn voltage drop to sluggish lower sideband V _{HYS_L}The time, S _HConducting, S _LTurn-off, make C _AddOn voltage V _FBRise.Ignoring capacitor C _AddVoltage ripple and internal system delay etc. ideally, switching frequency can be expressed as simply:

$f_s=\frac{1}{R_{\mathrm{add}}{C}_{\mathrm{add}}\mathrm{\Δ}{V}_{\mathrm{HYS}}}\×\frac{V_{\mathrm{REF}}(V_{\mathrm{IN}}-V_{\mathrm{REF}})}{V_{\mathrm{IN}}}---\left(1\right)$

The AHWC control technology of invention can make sluggish Mode B UCK converter produce one according to input voltage adapting ground and be proportional to

Retarding window keeping the relatively stable of switching frequency, eliminate input voltage and change the influence that switching frequency is caused, realize control certainly frequently.The circuit of AHWC control is realized mainly comprising two parts shown in Fig. 4,5: retarding window produces circuit settling time, produces circuit as Fig. 4 and retarding window sideband, as Fig. 5.Retarding window produces T settling time that circuit is used to produce retarding window settling time _{HYS_ON}, i.e. switch S among Fig. 5 ₁And S ₂ON time; The retarding window sideband produces upper sideband and the lower sideband that circuit is used to produce retarding window, i.e. voltage V among Fig. 5 _{HYS_H}And V _{HYS_L}The concrete analysis of AHWC control circuit is as follows:

In Fig. 4, k is the feedback resistance ratio of amplifier AMP.AMP detects input voltage and output reference voltage V _REFDifference, produce a threshold voltage V who is proportional to this difference at the positive input terminal of comparator C OMP then _CP, can be expressed as:

$V_{\mathrm{CP}}=\frac{V_{\mathrm{IN}}-V_{\mathrm{REF}}}{k}---\left(2\right)$

And, capacitor C _TBy internal current source I _TCharging.I _TThe current source that is made of unity gain amplifier and current mirror provides, and can be expressed as:

$I_T=\frac{a{V}_{\mathrm{IN}}}{R_{1}m}---\left(3\right)$

In the formula (3), a is a proportionality constant, and m is the image ratio of current mirror.And, the negative input end voltage V of comparator C OMP _CNCan be expressed as:

$V_{\mathrm{CN}}=\frac{I_{T}t}{C_T}+I_T{R}_T---\left(4\right)$

Wherein, resistance R _TBe used to regulate T _{HYS_ON}Actual output accuracy.Work as V _CNLess than V _CPThe time, COMP will export high level, then T _{HYS_ON}Can be expressed as:

$T_{\mathrm{HYS}\_\mathrm{ON}}=\frac{C_T{V}_{\mathrm{CP}}}{I_T}-C_T{R}_T+T_{\mathrm{DEL}\_\mathrm{COMP}}---\left(5\right)$

In the formula (5), T _{DEL_COMP}The propagation delay time of expression comparator C OMP.If select R _TMake C _TWith R _TProduct just equal T _{DEL_COMP}, then have:

$T_{\mathrm{HYS}\_\mathrm{ON}}=\frac{C_T{V}_{\mathrm{CP}}}{I_T}---\left(6\right)$

Get retarding window T settling time by formula (2), (3) and (6) _{HYS_ON}Finally can be expressed as:

$T_{\mathrm{HYS}\_\mathrm{ON}}=\frac{C_T{R}_{1}m}{\mathrm{ka}}\×\frac{V_{\mathrm{IN}}-V_{\mathrm{REF}}}{V_{\mathrm{IN}}}---\left(7\right)$

In Fig. 5, capacitor C _HYS1And C _HYS2By internal current source I _HYSCharging.I _HYSThe current source that is made of unity gain amplifier and current mirror provides, and can be expressed as:

$I_{\mathrm{HYS}}=\frac{{\mathrm{bV}}_{\mathrm{REF}}}{R_{2}n}---\left(8\right)$

In the formula (8), b is a proportionality constant, and n is the image ratio of current mirror.Switch S ₁And S ₂Respectively as capacitor C _HYS1And C _HYS2Charging control switch, and with S ₁And S ₂ON time be set to retarding window T settling time _{HYS_ON}, V then _{HYS_H}And V _{HYS_L}Can be expressed as respectively:

$V_{\mathrm{HYS}\_H}=\frac{I_{\mathrm{HYS}}{T}_{\mathrm{HYS}\_\mathrm{ON}}}{{\mathrm{<figure-callout\; id="1"\; label="C\; HYS"\; filenames="HDA0000048054950000022.png,HDA0000048054950000023.png"\; state="\{\{state\}\}">C</figure-callout>}}_{\mathrm{HYS}}}+V_{\mathrm{REF}}---\left(9\right)$

$V_{\mathrm{HYS}\_L}=V_{\mathrm{REF}}-\frac{I_{\mathrm{HYS}}{T}_{\mathrm{HYS}\_\mathrm{ON}}}{C_{\mathrm{HYS}2}}---\left(10\right)$

If with V _{HYS_H}And V _{HYS_L}Respectively as the upper sideband and the lower sideband of retarding window, and make C _HYS1=C _HYS2=C _HYS, retarding window Δ V then _HYSCan be expressed as:

$\mathrm{\&Delta;}{V}_{\mathrm{HYS}}=V_{\mathrm{HYS}\_H}-V_{\mathrm{HYS}\_L}=2\frac{I_{\mathrm{HYS}}{T}_{\mathrm{HYS}\_\mathrm{ON}}}{C_{\mathrm{HYS}}}---\left(11\right)$

Get retarding window Δ V by formula (7), (8) and (11) _HYSFinally can be expressed as:

$\mathrm{\&Delta;}{V}_{\mathrm{HYS}}=2\frac{{\mathrm{bmR}}_1{C}_T}{\mathrm{kan}{R}_2{C}_{\mathrm{HYS}}}\&times;\frac{V_{\mathrm{REF}}(V_{\mathrm{IN}}-V_{\mathrm{REF}})}{V_{\mathrm{IN}}}---\left(12\right)$

As the formula (12), retarding window Δ V _HYSBe proportional to

If choose suitable system parameters, switching frequency just can preestablish, and eliminates the influence of input voltage to switching frequency.

In actual applications, change and internal switch S for fear of input voltage ₁And S ₂Leakage Current to capacitor C _HYS1And C _HYS2On sluggish sideband voltage V _{HYS_H}And V _{HYS_L}Impact, the AHWC control circuit is by increasing switch S _T, S ₃And S ₄, shown in Fig. 4,5, (Periodic Refresh Mechanism PSM), periodically refreshes with sustaining voltage V two sluggish sidebands of retarding window to have designed sluggish sideband periodic refresh mechanism _{HYS_H}And V _{HYS_L}Size and input voltage V _INCorresponding, promptly keep retarding window Δ V _HYSSize and input voltage V _INCorresponding, crucial control waveform as shown in Figure 6.When a switch periods has just begun, switch S _TConducting is with capacitor C _TOn the voltage ground of releasing so that produce new retarding window T settling time _{HYS_ON}Simultaneously, switch S ₃And S ₄Conducting is respectively with voltage V _{HYS_H}And V _{HYS_L}Output reference voltage V releases _REFThen, switch S ₁And S ₂Conducting (this moment switch S _T, S ₃And S ₄Turn-off) respectively to capacitor C _HYS1And C _HYS2Again charge.Elapsed time T _{HYS_ON}After, switch S ₁And S ₂Turn-off.Like this, two new sluggish sideband V _{HYS_H}And V _{HYS_L}, i.e. new being proportional to

Retarding window just rebulid.

In addition, for guarantee converter can be in specified input voltage range maintained switch frequency relatively stable, the settling time of retarding window _{THYS_ON}Must be less than converter main switch S _HON time T _{D_ON}, as shown in Figure 6.In the ideal case, for the BUCK converter, T _{D_ON}Equal duty ratio D and switch periods T _SProduct.By rational system design and suitable selection of parameter, adopt the sluggish Mode B UCK converter of the AHWC control technology of invention just can be in certain input voltage range the maintained switch frequency relatively stable, reach certainly frequently and control.

The described content of this specification embodiment only is enumerating the way of realization of inventive concept; protection scope of the present invention should not be regarded as only limiting to the concrete form that embodiment states, protection scope of the present invention also reach in those skilled in the art conceive according to the present invention the equivalent technologies means that can expect.

Claims (4)

1. sluggish pattern voltage-dropping type DC/DC switch converters, comprise input voltage source, output inductor that is connected in parallel and output filter capacitor, be arranged at the main switch between output inductor and the input voltage source, be arranged at the synchro switch between output inductor and the ground, hysteresis comparator and can produce the non-intersect switching drive signal that changes, avoid the Dead Time of main switch and synchro switch while conducting to control and driver module; The output of described hysteresis comparator is connected with the input of described Dead Time control and driver module;

It is characterized in that: also have in the described switch converters and can produce the retarding window control module of a retarding window according to input voltage adapting ground with the stable switch frequency, input voltage and output reference voltage are all imported in the described retarding window control module, and upper sideband voltage and lower sideband voltage that described retarding window control module produces are imported respectively in the positive input terminal of hysteresis comparator;

The output voltage of switch transformer is imported in the negative input end of described hysteresis comparator by coupling resistance, one end of the close output filter capacitor of described main switch is connected with branch road resistance, described branch road resistance and branch road capacitances in series, one end of the close branch road electric capacity of described branch road resistance is connected with an end of the close described hysteresis comparator of described coupling resistance, described branch road capacity earth.

2. sluggish pattern voltage-dropping type DC/DC switch converters as claimed in claim 1, it is characterized in that: described retarding window control module comprises retarding window generation unit settling time and retarding window sideband generation unit;

Described retarding window generation unit settling time comprises the amplifier of the threshold voltage that the difference of obtaining input voltage and output reference voltage and output are proportional to described difference, comparator and first internal current source of negative input end voltage is provided for comparator; The threshold voltage of described amplifier output is as the positive input terminal voltage of described comparator;

Described first internal current source is made of first unity gain amplifier and first current mirror, and described internal current source and first internal capacitance and the adjusting resistance that can regulate the actual output accuracy of retarding window settling time are connected; One end of close described first current mirror of described adjusting resistance is connected with the negative input end of described comparator;

When threshold voltage during greater than negative input end voltage, described comparator output high level; When threshold voltage during less than negative input end voltage, described comparator output low level;

Described retarding window sideband generation unit comprises second internal current source and first switch that is connected in series, upper sideband electric capacity, lower sideband electric capacity and second switch; Described upper sideband electric capacity and the 3rd switch in parallel; Described lower sideband electric capacity and the 4th switch in parallel, described first switch and second switch are controlled by retarding window settling time, voltage between first switch and the upper sideband electric capacity is upper sideband voltage, and the voltage between second switch and the lower sideband electric capacity is lower sideband voltage;

Described second internal current source is made of two current mirrors and a unity gain amplifier.

3. sluggish pattern voltage-dropping type DC/DC switch converters as claimed in claim 2, it is characterized in that: the internal capacitance of described retarding window generation module settling time is in parallel with capacitance switch.

4. sluggish pattern voltage-dropping type DC/DC switch converters as claimed in claim 3, it is characterized in that: described input voltage source is in parallel with the input voltage filter capacitor, described input voltage filter capacitor ground connection.

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