CN202918193U

CN202918193U - Bootstrap voltage refresh control circuit and voltage conversion circuit

Info

Publication number: CN202918193U
Application number: CN 201220437368
Authority: CN
Inventors: 李伊珂
Original assignee: Chengdu Monolithic Power Systems Co Ltd
Current assignee: Chengdu Monolithic Power Systems Co Ltd
Priority date: 2012-08-30
Filing date: 2012-08-30
Publication date: 2013-05-01
Anticipated expiration: 2022-08-30

Abstract

A bootstrap voltage refresh control circuit and a voltage conversion circuit are provided. The bootstrap voltage refresh control circuit detects a bootstrap voltage in the voltage conversion circuit, provides enhanced on and off driving signals for a high-side switch of the voltage conversion circuit based on the bootstrap voltage, and controls charging of the bootstrap voltage by controlling on and off switching of the high-side switch and a low-side switch of the voltage conversion circuit based on the bootstrap voltage. The bootstrap voltage refresh control circuit can timely recover the bootstrap voltage by adjusting the on and off switching of the high-side switch and the low-side switch when the bootstrap voltage is insufficient, and can be realized without adding more switching devices. The voltage conversion circuit comprising the bootstrap voltage refresh control circuit has good working stability, can still work normally when the input voltage and the output voltage of the voltage conversion circuit are relatively close to each other, and has small power consumption.

Description

Bootstrap voltage mode refresh control circuit and voltage conversion circuit

Technical field

Embodiment of the present utility model relates to power inverter, relates in particular to the bootstrap voltage mode refresh control circuit in the power inverter.

Background technology

Power inverter, for example the switching mode electric pressure converter has been widely used in various industrial electrical equipment and the consumer-elcetronics devices.Take the step-down type dc electric pressure converter as example, because it has higher conversion efficiency, larger bandwidth and is easy to realize stabiloity compensation, and often be applied to needing relatively high DC input voitage is converted to the occasion of relatively low VD.Fig. 1 shows a kind of rough schematic view of typical step-down type dc voltage conversion circuit 50.In brief, step-down type dc voltage conversion circuit 50 receives input voltage vin by input IN, and by control circuit 51 control high-side switch M _HS(being illustrated as MOSFET among Fig. 1) and low side switch M _LSConducting and the shutoff of (being illustrated as MOSFET among Fig. 1) are to realize that input voltage vin is converted to suitable output voltage V o in the purpose of its output OUT output.Wherein, high-side switch M _HS(being illustrated as MOSFET among Fig. 1) and low side switch M _LSBe coupled in series between input IN and the reference ground GND, and high-side switch M _HSWith low side switch M _LSThe SW (being switched voltage output SW) that couples be coupled to output OUT by perceptual energy-storage travelling wave tube Lo, capacitive energy-storage travelling wave tube Co be coupled in output OUT and with reference to ground GND between with smooth output voltage Vo.

High-side switch M _HSCan comprise N channel power switching device, such as N channel fet, N raceway groove DMOS etc. to save chip area, reduce the size of voltage conversion circuit 50 and to improve the service behaviour of voltage conversion circuit 50.In this case, in order to make high-side switch M _HSWell conducting (means and makes M _HSBe operated in the saturation region, like this M _HSConducting resistance very little), high-side switch M _HSControl end (for example grid end of FET/DMOS) and the voltage difference between its end (for example source of FET/DMOS) that couples the SW node should be enough large, at least greater than high-side switch M _HSOn state threshold voltage.Yet, if high-side switch M _HSConducting, the voltage of SW node can be input voltage vin, at this moment, need to be high-side switch M _HSControl end the voltage that is higher than the SW node is provided, namely be higher than input voltage vin, voltage just can make high-side switch M _HSFully conducting.

In order to obtain to be higher than the voltage of input voltage vin in step-down type dc voltage conversion circuit 50, step-down type dc voltage conversion circuit 50 also comprises boostrap circuit 52 usually, is used for producing bootstrap voltage mode V take the voltage of SW node as reference potential _BST, this bootstrap voltage mode V _BSTCan be used for promoting/strengthening by control circuit 51 is high-side switch M _HSThe control signal DR that provides of control end _HDriving force, thereby control well high-side switch M _HSTurn-on and turn-off.Among Fig. 1 boostrap circuit 52 is illustrated as and comprises diode DB and bootstrap capacitor CB, coupled in series is between bootstrapping is for electrical input VB and switched voltage output SW, wherein the negative electrode of diode DB couples bootstrapping for electrical input VB, the anode of diode DB couples the first end of bootstrap capacitor CB, the second end of bootstrap capacitor CB couples switched voltage output SW, bootstrapping receives the bootstrapping supply power voltage for electrical input VB, and the voltage between bootstrap capacitor CB first end and the second end is bootstrap voltage mode V _BSTThe operation principle of boostrap circuit 52 is that those of ordinary skill in the art is known, that is, and and as high-side switch M _HSDuring shutoff, low side switch M _LSConducting, the bootstrapping supply power voltage is bootstrap capacitor CB charging by diode DB, so that have bootstrap voltage mode V between bootstrap capacitor CB first end and the second end _BSTAs high-side switch M _HSDuring conducting, low side switch M _LSTurn-off, the input voltage vin in the voltage conversion circuit 50 is transferred to switched voltage output SW, and namely the voltage of bootstrap capacitor the second end becomes Vin, then this moment bootstrap capacitor CB first end voltage be lifted as input voltage vin and be superimposed with bootstrap voltage mode V _BSTThereby, realized in step-down type dc voltage conversion circuit 50 obtaining being higher than the purpose of the voltage of input voltage vin.The voltage of bootstrap capacitor CB first end is lifted as input voltage vin and is superimposed with bootstrap voltage mode V _BSTAfter, diode DB reverse bias and being turned off, thus can protect the power supply that the bootstrapping supply power voltage is provided not to be subjected to the damage of relatively high input voltage vin.

As seen, boostrap circuit 52 passes through at low side switch M _LSVoltage with bootstrap capacitor CB the second end during conducting is pulled low to reference to ground, and obtains the chance for bootstrap capacitor CB charging, so that bootstrap voltage mode V to be provided _BSTYet under some operating state, may and can not in time be charged to enough levels owing to the deficiency of the electric charge on the bootstrap capacitor CB, and the bootstrap voltage mode V that causes boostrap circuit 52 to provide _BSTDescend, deficiency is so that high-side switch M _HSNormally and shutoff, so also therefore cisco unity malfunction of voltage conversion circuit 50.For example: if voltage conversion circuit 50 is operated in the lighter or unloaded situation of load, then control circuit 51 can reduce high-side switch M _HSWith low side switch M _LSON time and/or switching frequency to improve conversion efficiency, like this may be owing to low side switch M _LSThe very short or high-side switch M of ON time _HSWith low side switch M _LSDo not carry out in a long time the turn-on and turn-off switching and bootstrap capacitor CB is in time charged.In addition, if the output voltage V o of voltage conversion circuit 50 near input voltage vin, then may need high-side switch M _HSDuty ratio work (that is, high-side switch M with very high even 100% _HSON time sizable ratio or even full cycle that may account for whole switching cycle), low side switch M so _LSON time just very short even do not have the conducting chance, and bootstrap capacitor CB can't in time be charged.After will waiting until that like this output voltage V o reduces, bootstrap capacitor CB just has an opportunity to be recharged so that bootstrap voltage mode V _BSTRecover, this can cause that the fluctuation spike appears in output voltage V o.For example, if input voltage vin is 6V, output voltage V o is 3.3V, and bootstrap voltage mode V _BSTBe at least 3V and just enough allow high-side switch M _HSNormally and shutoff.In this case, if the output current of voltage conversion circuit 50 is less or be zero (that is, voltage conversion circuit 50 is operated in the lighter or unloaded situation of load), bootstrap voltage mode V _BSTWill inevitably be brought down below 2.7V, and make high-side switch M _HSCan't normally.So, voltage conversion circuit 50 need to wait until that output voltage V o is reduced to less than behind the 3V, just has an opportunity to make bootstrap capacitor CB charge to allow bootstrap voltage mode V _BSTReturn to 3V.Then voltage conversion circuit 50 normal operations make output voltage V o get back to the desired value of 3.3V.Each output voltage V o be by larger fluctuation spike can occurring in the process that is lower than 3V and returns to 3.3V, and this not only more likely damages load to voltage conversion circuit 50 is unfavorable, thereby does not wish to occur.

The utility model content

For one or more problems of the prior art, embodiment of the present utility model provides a kind of bootstrap voltage mode refresh control circuit and voltage conversion circuit.

Aspect one of the present utility model, a kind of bootstrap voltage mode refresh control circuit has been proposed, be used for voltage conversion circuit, wherein said voltage conversion circuit comprises high-side switch and low side switch and is used to described high-side switch that the bootstrap capacitor of bootstrap voltage mode is provided, described voltage conversion circuit switches based on the turn-on and turn-off of described high-side switch and low side switch provides output voltage and output current, described bootstrap voltage mode refresh control circuit comprises: the first comparison module, have first and compare input, second compares relatively output of input and first, wherein said first compares input is used for receiving described bootstrap voltage mode, described second relatively input be used for receiving bootstrap voltage mode and refresh threshold value, described the first comparison module is used for described bootstrap voltage mode and described bootstrap voltage mode refreshed that threshold value compares and compare output described first provides the bootstrap voltage mode refresh signal; And control module, having the first control input end and be used for receiving described bootstrap voltage mode refresh signal, the conducting of controlling described high-side switch and described low side switch based on described bootstrap voltage mode refresh signal is switched to control the charging of described bootstrap capacitor with shutoff.

According to embodiment of the present utility model, described control module also has the second control input end and the 3rd control input end, wherein said the second control input end is for detection of the output voltage of described voltage conversion circuit, and described the 3rd control input end is for detection of the output current of described voltage conversion circuit; Refresh threshold value if described bootstrap voltage mode is lower than described bootstrap voltage mode, described bootstrap voltage mode refresh signal has the first logic state, refreshes threshold value if described bootstrap voltage mode is higher than described bootstrap voltage mode, and described bootstrap voltage mode refresh signal has the second logic state; If described bootstrap voltage mode refresh signal has the first logic state, described control module is controlled described high-side switch and described low side switch based on described bootstrap voltage mode refresh signal and is carried out turn-on and turn-off with the frequency complementary ground of constant and switch, and thinks described charging bootstrap capacitor; If described bootstrap voltage mode refresh signal has the second logic state, described control module controls described high-side switch based on described bootstrap voltage mode refresh signal and described low side switch carries out the turn-on and turn-off switching according to described output voltage and described output current.

According to embodiment of the present utility model, described bootstrap voltage mode refreshes threshold value and comprises that first refreshes threshold value and second and refresh threshold value, and wherein said first refreshes threshold value refreshes threshold value less than described second; Refresh threshold value if described bootstrap voltage mode is lower than described first, described bootstrap voltage mode refresh signal has the first logic state; Refresh threshold value if described bootstrap voltage mode is higher than described second, described bootstrap voltage mode refresh signal has the second logic state.

According to embodiment of the present utility model, described control module comprises: the second comparison module, has the input of enabling, the 3rd compares input, the 4th compares relatively output of input and second, the wherein said input that enables is used for receiving described bootstrap voltage mode refresh signal, the described the 3rd compares the load signal that input is used for receiving the output current that characterizes described voltage conversion circuit, the described the 4th relatively input be used for receiving the underloading threshold value, described the second comparison module is used for providing the load comparison signal with described load signal with described underloading threshold value compares and compare output described second; If being lower than described bootstrap voltage mode, described bootstrap voltage mode refreshes threshold value, described bootstrap voltage mode refresh signal is controlled described the second comparison module and is not enabled, refresh threshold value if described bootstrap voltage mode is higher than described bootstrap voltage mode, described bootstrap voltage mode refresh signal is controlled described the second comparison module and is enabled; If described the second comparison module enables, when described load signal was higher than described underloading threshold value, described load comparison signal had the first logic state, and when described load signal was lower than described underloading threshold value, described load comparison signal had the second logic state; If described the second comparison module does not enable, described load comparison signal constant ground has described the first logic state; If described load comparison signal has described the first logic state, described control module is carried out deciding the frequency conducting and turn-offing switching of pulse width modulation based on this duty ratio than the described high-side switch of signal controlling and described low side switch; If described load comparison signal has described the second logic state, described control module is carried out the frequency conversion conducting and shutoff switching of pulse frequency modulated than the described high-side switch of signal controlling and described low side switch based on this duty ratio.

According to embodiment of the present utility model, when described load comparison signal had described the first logic state, the conducting of described high-side switch and described low side switch was the first switching frequency of constant with turn-offing switching frequency; When described load comparison signal had described the second logic state, the conducting of described high-side switch and described low side switch was the second switching frequency that changes with turn-offing switching frequency; Wherein said the second switching frequency changes according to the variation of described load signal.

According to embodiment of the present utility model, described control module further comprises:

The pulse width modulation module, have the first modulation input, the second modulation input, the 3rd modulation input and modulation output, wherein said the first modulation input is used for receiving described load comparison signal, described the second modulation input is for detection of described output voltage, described the 3rd modulation input is for detection of described output current, and described modulation output provides high-side switch control signal and low side switch control signal based on described output voltage and described output current; And

Described pulse width modulation module according to described duty ratio than the described high-side switch control signal of Signal Regulation and described low side switch control signal, when described when the load comparison signal has the first logic state, described high-side switch control signal and described low side switch control signal keep pulse width modulation or are converted to pulse width modulation by pulse frequency modulated, make described high-side switch and described low side switch carry out deciding the frequency conducting and turn-offing switching of pulse width modulation; When described load comparison signal has the second logic state, described high-side switch control signal and described low side switch control signal are converted to pulse frequency modulated by pulse width modulation, and the frequency conversion conducting that makes described high-side switch and described low side switch carry out pulse frequency modulated is switched with shutoff.

According to embodiment of the present utility model, when described load comparison signal had the first logic state, the frequency turn-on and turn-off of deciding that described pulse width modulation module controls high-side switch and low side switch carry out pulse width modulation were switched; When described load comparison signal had the second logic state, the described high-side switch of described pulse width modulation module controls and described low side switch turn-offed, and stopped turn-on and turn-off and switched.

According to embodiment of the present utility model, described pulse width modulation module comprises:

The pulse width modulating signal circuit for generating receives the first feedback signal that characterizes described output voltage and the second feedback signal that characterizes described output current, and provides pulse width modulating signal based on described the first feedback signal and described the second feedback signal;

The switching frequency control circuit, receive described load comparison signal, and provide the switching frequency modulation signal based on this load comparison signal, when this load comparison signal has the first logic state, the switching frequency modulation signal has the first switching frequency of constant, when this load comparison signal had the second logic state, the switching frequency modulation signal had the second switching frequency that changes with described load signal; With

Logic control circuit receives described pulse width modulating signal and described switching frequency modulation signal, and provides described high-side switch control signal and described low side switch control signal based on described pulse width modulating signal and described switching frequency modulation signal; When described load comparison signal has the first logic state, described high-side switch control signal and described low side switch control signal are the pulse width modulating signal with described first switching frequency, carry out deciding the frequency conducting and turn-offing switching of pulse width modulation for controlling described high-side switch and described low side switch; When described load comparison signal has the second logic state, described high-side switch control signal and described low side switch control signal are the pulse frequency modulated signal with described second switching frequency, are used for frequency conversion conducting and shutoff switching that control high-side switch and low side switch carry out pulse frequency modulated.

According to embodiment of the present utility model, described bootstrap voltage mode refresh control circuit further comprises:

The zero passage detection module, having first detects input, the second detection input and detects output, wherein said first detects input is used for receiving the 3rd feedback signal that characterizes the electric current that flows through described low side switch, described second detects input is used for receiving the low side switch current limit threshold, and described detection output is used for providing the zero passage comparison signal according to the comparative result of described the 3rd feedback signal and described low side switch current limit threshold;

When described the 3rd feedback signal was higher than described low side switch current limit threshold, described zero passage comparison signal had the first logic state, and when described the 3rd feedback signal was lower than described low side switch current limit threshold, described zero passage comparison signal had the second logic state;

When described zero passage comparison signal has the first logic state, described bootstrap voltage mode refresh control circuit allows described low side switch to carry out the turn-on and turn-off switching based on this zero passage comparison signal, when described zero passage comparison signal has the second logic state, described bootstrap voltage mode refresh control circuit turn-offs described low side switch based on this zero passage comparison signal, makes it stop turn-on and turn-off and switches.

According to embodiment of the present utility model, what described low side switch current limit threshold had a setting is lower than zero and close to zero offset.

The under-voltage block of valve circuit of booting, have the first block of valve input, the second block of valve input and block of valve output, wherein said the first block of valve input is used for receiving described bootstrap voltage mode, described the second block of valve input is used for receiving bootstrapping under-voltage threshold value, and the under-voltage threshold value of described bootstrap voltage mode refreshes threshold value less than described bootstrap voltage mode, described bootstrapping is under-voltage, and block of valve circuit is used for described bootstrap voltage mode and the under-voltage threshold of described bootstrap voltage mode, and provides bootstrapping under-voltage signal at described block of valve output;

If described bootstrap voltage mode is lower than the under-voltage threshold value of described bootstrap voltage mode, the under-voltage signal of described bootstrapping has the first logic state, if described bootstrap voltage mode is higher than the under-voltage threshold value of described bootstrap voltage mode, the under-voltage signal of described bootstrapping has the second logic state;

When the under-voltage signal of described bootstrapping had the first logic state, described bootstrap voltage mode refresh control circuit turn-offed described high-side switch and described low side switch based on this under-voltage signal of booting, and stops conducting and turn-offs switching; When the under-voltage signal of described bootstrapping had the second logic state, described bootstrap voltage mode refresh control circuit allowed described high-side switch and described low side switch to carry out the turn-on and turn-off switching based on this under-voltage signal of booting.

On the other hand of the present utility model, a kind of voltage conversion circuit has been proposed, comprising: input is used for receiving input voltage; Output is used for providing output voltage and output current; High-side switch and low side switch, coupled in series in described input with reference to ground between, and coupling of described high-side switch and described low side switch forms a switched voltage output; Output filter circuit is coupled between described switched voltage output and the described output, is used for the switched voltage of described switched voltage output is converted into described output voltage; Boostrap circuit comprises bootstrap capacitor, couples described input and described low side switch, so that described bootstrap capacitor charges to produce bootstrap voltage mode when described low side switch conducting; And control circuit, receive described bootstrap voltage mode, provide the conducting of enhancing to drive signal with shutoff based on this bootstrap voltage mode for described high-side switch, and switch to control the charging of described bootstrap capacitor based on this bootstrap voltage mode by the turn-on and turn-off of controlling described high-side switch and described low side switch.

According to embodiment of the present utility model, described control circuit comprises: the first comparison module, have the first comparison input, second relatively input and the first comparison output, wherein said first compares input is used for receiving described bootstrap voltage mode, described second relatively input be used for receiving bootstrap voltage mode and refresh threshold value, described the first comparison module is used for described bootstrap voltage mode and described bootstrap voltage mode refreshed that threshold value compares and compare output described first provides the bootstrap voltage mode refresh signal; And control module, having the first control input end and be used for receiving described bootstrap voltage mode refresh signal, the conducting of controlling described high-side switch and described low side switch based on described bootstrap voltage mode refresh signal is switched to control the charging of described bootstrap capacitor with shutoff.

According to embodiment of the present utility model, described control module also has the second control input end and the 3rd control input end, wherein said the second control input end is for detection of the output voltage of described voltage conversion circuit, and described the 3rd control input end is for detection of the output current of described voltage conversion circuit;

Refresh threshold value if described bootstrap voltage mode is lower than described bootstrap voltage mode, described bootstrap voltage mode refresh signal has the first logic state, refreshes threshold value if described bootstrap voltage mode is higher than described bootstrap voltage mode, and described bootstrap voltage mode refresh signal has the second logic state;

If described bootstrap voltage mode refresh signal has the first logic state, described control module is controlled described high-side switch and described low side switch based on described bootstrap voltage mode refresh signal and is carried out turn-on and turn-off with the frequency complementary ground of constant and switch, and thinks described charging bootstrap capacitor; If described bootstrap voltage mode refresh signal has the second logic state, described control module controls described high-side switch based on described bootstrap voltage mode refresh signal and described low side switch carries out the turn-on and turn-off switching according to described output voltage and described output current.

According to embodiment of the present utility model, described control module comprises:

The second comparison module, have the input of enabling, the 3rd comparison input, the 4th relatively input and the second comparison output, the wherein said input that enables is used for receiving described bootstrap voltage mode refresh signal, the described the 3rd compares the load signal that input is used for receiving the output current that characterizes described voltage conversion circuit, the described the 4th relatively input be used for receiving the underloading threshold value, described the second comparison module is used for providing the load comparison signal with described load signal with described underloading threshold value compares and compare output described second; Be further characterized in that,

If being lower than described bootstrap voltage mode, described bootstrap voltage mode refreshes threshold value, described bootstrap voltage mode refresh signal is controlled described the second comparison module and is not enabled, refresh threshold value if described bootstrap voltage mode is higher than described bootstrap voltage mode, described bootstrap voltage mode refresh signal is controlled described the second comparison module and is enabled;

If described the second comparison module enables, when described load signal was higher than described underloading threshold value, described load comparison signal had the first logic state, and when described load signal was lower than described underloading threshold value, described load comparison signal had the second logic state;

If described the second comparison module does not enable, described load comparison signal constant ground has described the first logic state; Be further characterized in that,

If described load comparison signal has described the first logic state, described control module is carried out deciding the frequency conducting and turn-offing switching of pulse width modulation based on this duty ratio than the described high-side switch of signal controlling and described low side switch;

If described load comparison signal has described the second logic state, described control module is carried out the frequency conversion conducting and shutoff switching of pulse frequency modulated than the described high-side switch of signal controlling and described low side switch based on this duty ratio.

According to embodiment of the present utility model, described voltage conversion circuit further comprises:

The zero passage detection module, having first detects input, the second detection input and detects output, wherein said first detects input is used for receiving the 3rd feedback signal that characterizes the electric current that flows through described low side switch, described second detects input is used for receiving the low side switch current limit threshold, and described detection output is used for providing the zero passage comparison signal according to the comparative result of described the 3rd feedback signal and described low side switch current limit threshold; Be further characterized in that,

When described the 3rd feedback signal was higher than described low side switch current limit threshold, described zero passage comparison signal had the first logic state, and when described the 3rd feedback signal was lower than described low side switch current limit threshold, described zero passage comparison signal had the second logic state; Be further characterized in that

When described zero passage comparison signal has the first logic state, described control circuit allows described low side switch to carry out the turn-on and turn-off switching based on this zero passage comparison signal, when described zero passage comparison signal has the second logic state, described control circuit turn-offs described low side switch based on this zero passage comparison signal, makes it stop turn-on and turn-off and switches.

Utilize such scheme, bootstrap voltage mode refresh control circuit according to the utility model embodiment in time makes this bootstrap voltage mode recover by the conducting of adjusting high-side switch and low side switch with turn-offing switching when bootstrap voltage mode is not enough, need not to increase more switching devices and just can realize.The voltage conversion circuit that comprises this bootstrap voltage mode refresh control circuit has good job stability, its input voltage and output voltage relatively near the time still can work, and power consumption is less.

Description of drawings

Below accompanying drawing help to understand better next description to the different embodiment of the utility model.These accompanying drawings are not feature, size and the scale according to reality, but schematically show the principal character of some execution modes of the utility model.These drawings and embodiments provide embodiment more of the present utility model in the mode of non-limiting, non exhaustive property.For simplicity's sake, the identical or similar assembly or the structure that have identical function in the different accompanying drawings adopt identical Reference numeral.

Fig. 1 shows a kind of rough schematic view of typical step-down type dc voltage conversion circuit 50;

Fig. 2 shows the circuit framework schematic diagram according to the voltage conversion circuit 100 of an embodiment of the utility model;

Fig. 3 shows the circuit framework schematic diagram according to the voltage conversion circuit 200 of an embodiment of the utility model;

Fig. 4 shows the configuration diagram according to the switching frequency control circuit of an embodiment of the utility model;

Fig. 5 shows the groundwork waveform schematic diagram according to the as shown in Figure 3 voltage conversion circuit 200 of an embodiment of the utility model.

Embodiment

The below will describe embodiment more of the present utility model in detail.In ensuing explanation, some concrete details, for example the design parameter of the particular circuit configurations among the embodiment and these circuit elements all is used for providing better understanding to embodiment of the present utility model.Even those skilled in the art are appreciated that embodiment of the present utility model also can be implemented in the situation that lacks the combinations such as some details or additive method, element, material.

In specification of the present utility model, specific features, structure or the parameter that all means when mentioning " embodiment " to describe in this embodiment, step etc. are included at least according among the embodiment of the present utility model.Thereby, in specification of the present utility model, refer in particular in same embodiment if adopted terms such as " according to an embodiment of the present utility model ", " in one embodiment " and be not used in, if adopted terms such as " in a further embodiment ", " according to different embodiment of the present utility model ", " embodiment other according to the utility model ", also and be not used in and refer in particular to the feature of mentioning and to be included among the specific different embodiment.It should be appreciated by those skilled in the art that disclosed each specific features, structure or parameter, step etc. can make up in any suitable manner in one or more embodiment of the utility model specification.In addition, in specification of the present utility model and claim, " coupling " word means to realize directly or indirectly connection by electric or non-electric mode." one " also is not used in and refers in particular to singlely, but can comprise plural form." ... in " can comprise " and ... in " and " ... on " implication.Unless explicitly point out especially, "or" can comprise "or", " with " reach " or/and " implication, and be not used in and refer in particular to one that to select in several features arranged side by side, but mean to select one of them or the several or wherein combination of certain several feature.Unless explicitly point out especially, " based on " word do not have exclusiveness, but mean except based on the feature of clearly describing, can also be based on other feature of clearly not describing." circuit " means to be coupled in together so that the structure of specific function to be provided to one or more active or passive element of major general." signal " can refer to comprise the signal of electric current, voltage, electric charge, temperature, data, pressure or other type at least.If the embodiment of " transistor " can comprise " field-effect transistor " or " bipolar junction transistor ", then " grid/grid region ", " source electrode/source region ", " drain electrode/drain region " can comprise respectively " base stage/base ", " emitter/emitter region ", " collector electrode/collector region ", and vice versa.It should be appreciated by those skilled in the art that the explanation to describing term in the utility model of more than enumerating only is exemplary, and be not used in each term is carried out absolute restriction.

Fig. 2 shows the circuit framework schematic diagram according to the voltage conversion circuit 100 of an embodiment of the utility model.This voltage conversion circuit 100 comprises: input IN is used for receiving input voltage vin; Output OUT is used for providing output voltage V o and output current Io; High-side switch M _HSWith low side switch M _LS, coupled in series is between input IN and reference ground GND, and high-side switch M _HSWith low side switch M _LSCouple and to form a switched voltage output SW; Output filter circuit 101 is coupled between switched voltage output SW and the output OUT, is used for the switched voltage V with switched voltage output SW place _SWBe converted into output voltage V o; Boostrap circuit 102 comprises bootstrap capacitor CB, couples input IN and low side switch M _LS, so that bootstrap capacitor CB is at low side switch M _LSBe recharged to produce bootstrap voltage mode V during conducting _BSTControl circuit 103 receives bootstrap voltage mode V _BST, based on this bootstrap voltage mode V _BSTBe high-side switch M _HSProvide the conducting of enhancing to drive signal DR with shutoff _H, and based on this bootstrap voltage mode V _BSTBy control high-side switch M _HSWith low side switch M _LSTurn-on and turn-off switch to control the charging of bootstrap capacitor CB.

According to an embodiment of the present utility model, control circuit 103 is with bootstrap voltage mode V _BSTRefresh threshold value Vth1 (first threshold voltage Vth1) with bootstrap voltage mode and compare, output bootstrap voltage mode refresh signal RFS.If bootstrap voltage mode V _BSTBe lower than bootstrap voltage mode and refresh threshold value Vth1, then show bootstrap voltage mode V _BSTToo low, thus control circuit 103 is based on this bootstrap voltage mode V _BSTThe conducting that provides drives signal DR with shutoff _HDriving force descend, can not drive high-side switch M _HSNormally.At this moment, control circuit 103 is based on this bootstrap voltage mode refresh signal RFS control high-side switch M _HSWith low side switch M _LSFrequency complementary ground with constant carries out the turn-on and turn-off switching, can make low side switch M like this _LSHave suitable ON time at each switching cycle, think bootstrap capacitor CB charging.So, through behind the switching cycle of some, bootstrap voltage mode V _BSTIncrease gradually, until bootstrap voltage mode V _BSTBe higher than bootstrap voltage mode and refresh threshold value Vth1.If bootstrap voltage mode V _BSTBe higher than bootstrap voltage mode and refresh threshold value Vth1, then show this bootstrap voltage mode V _BSTEnough large, control circuit 103 can be based on this bootstrap voltage mode V _BSTProvide the conducting of enhancing to drive signal DR with shutoff _H, drive high-side switch M _HSFully conducting, at this moment, control circuit 103 is based on this bootstrap voltage mode refresh signal RFS control high-side switch M _HSWith low side switch M _LSLoad condition (states such as heavy duty, underloading and zero load) according to output voltage V o and output OUT carries out the turn-on and turn-off switching.

According to an embodiment of the present utility model, if bootstrap voltage mode V _BSTBe higher than bootstrap voltage mode and refresh threshold value Vth1, then control circuit 103 is based on this bootstrap voltage mode refresh signal RFS control high-side switch M _HSWith low side switch M _LSCarry out the turn-on and turn-off switching according to output voltage V o and output current Io.This is that output current Io is larger to show that then the load of output OUT is heavier because output current Io in fact can characterize the load condition of output OUT, and output current Io is less to show that then the load of output OUT is lighter.For example, if output current Io is larger, show that then the load of output OUT is heavier, if output current Io is less, show that then the load of output OUT is lighter, if output current Io is zero, show that then the load of output OUT is for unloaded.

Thereby according to each exemplary embodiment and modification execution mode thereof that the utility model is described based on Fig. 2, control circuit 103 is based on bootstrap voltage mode V _BSTControl high-side switch M _HSWith low side switch M _LSTurn-on and turn-off switch, with the charging of control bootstrap capacitor CB, thereby guarantee bootstrap voltage mode V _BSTEnough large, make the control circuit 103 can be based on this bootstrap voltage mode V _BSTProvide the conducting of enhancing to drive signal DR with shutoff _H, drive high-side switch M _HSFully conducting.Because 103 couples of high-side switch M of control circuit _HSWith low side switch M _LSThe turn-on and turn-off switching controls based on bootstrap voltage mode V _BST, thereby can be according to bootstrap voltage mode V _BSTState in time adjust high-side switch M _HSWith low side switch M _LSTurn-on and turn-off (for example: adjust high-side switch M switch _HSWith low side switch M _LSON time and turn-on and turn-off switching frequency), thereby at bootstrap voltage mode V _BSTWhen too low, in time for bootstrap capacitor CB charging, so that bootstrap voltage mode V _BSTCan in time recover.And according to each embodiment of the present utility model, need not to increase more switching devices and corresponding control circuit, but pass through based on bootstrap voltage mode V _BSTAdjust high-side switch M _HSWith low side switch M _LSTurn-on and turn-off switch, just can realize in time being bootstrap capacitor CB charging, with assurance bootstrap voltage mode V _BSTCan be used in and strengthen high-side switch M _HSConducting with turn-off to drive.

According to each exemplary embodiment and the modification execution mode thereof that the utility model is described based on Fig. 2, control circuit 103 detects bootstrap voltage mode V _BST, and pass through bootstrap voltage mode V _BSTRefreshing threshold value Vth1 with bootstrap voltage mode compares and judges bootstrap voltage mode V _BSTWhether too low; If bootstrap voltage mode V _BSTToo low (namely be lower than bootstrap voltage mode and refresh threshold value Vth1), no matter the load condition of voltage conversion circuit 100 how, such as heavy duty, underloading or unloaded etc., control circuit 103 is all controlled high-side switch M _HSWith low side switch M _LSFrequency complementary ground with constant carries out the turn-on and turn-off switching, so that low side switch M _LSHave suitable ON time at each switching cycle, thereby be bootstrap capacitor CB charging; If bootstrap voltage mode V _BSTNormally (namely be higher than bootstrap voltage mode and refresh threshold value Vth1), then control circuit 103 control high-side switch M _HSWith low side switch M _LSCarrying out turn-on and turn-off according to the load of output voltage V o and output OUT switches.For example: according to an embodiment of the present utility model, if bootstrap voltage mode V _BSTBe higher than bootstrap voltage mode and refresh threshold value Vth1, when the load of output OUT is heavier or normal, control circuit 103 control high-side switch M _HSWith low side switch M _LSThe constant frequency turn-on and turn-off of carrying out pulse width modulation according to the load of output voltage V o and output OUT are switched; Light or when be unloaded, control circuit 103 is controlled high-side switch M when the load of output OUT _HSWith low side switch M _LSCarry out the frequency conversion turn-on and turn-off switching of pulse frequency modulated according to the load condition of output voltage V o and output OUT, to reduce high-side switch M _HSWith low side switch M _LSSwitching frequency, thereby reduce the power consumption of voltage conversion circuit 100.

According to an embodiment of the present utility model, bootstrap voltage mode refreshes threshold value Vth1 (first threshold Vth1) can comprise that first refreshes threshold value Vth1 _LWith second refresh threshold value Vth1 _H, wherein said first refreshes threshold value Vth1 _LRefresh threshold value Vth1 less than described second _HIf bootstrap voltage mode V _BSTBe lower than first and refresh threshold value Vth1 _L, then control circuit 103 is based on described bootstrap voltage mode refresh signal RFS control high-side switch M _HSWith low side switch M _LSFrequency complementary ground with constant carries out the turn-on and turn-off switching.If bootstrap voltage mode V _BSTBe higher than second and refresh threshold value Vth1 _H, then control circuit 103 is based on described bootstrap voltage mode refresh signal RFS control high-side switch M _HSWith low side switch M _LSLoad condition according to output voltage V o and output OUT carries out the turn-on and turn-off switching.Refresh threshold value Vth1 first like this _LWith second refresh threshold value Vth1 _HBetween have certain sluggishness, can avoid because bootstrap voltage mode V _BSTMinor fluctuations and cause false triggering, thereby improve the job stability of voltage conversion circuit 100.

According to an embodiment of the present utility model, bootstrap capacitor CB is coupled between input IN and the switched voltage output SW, is used for the switched voltage V with switched voltage output SW place _SWFor reference potential produces bootstrap voltage mode V _BST, as low side switch M _LSDuring conducting, bootstrap capacitor CB is recharged to refresh bootstrap voltage mode V _BST

According to an embodiment of the present utility model, boostrap circuit 102 can also comprise bootstrapped switch DB, is coupled between input IN and the bootstrap capacitor CB bootstrapped switch DB and low side switch M _LSSynchronously conducting and shutoff.As low side switch M _LSDuring conducting, bootstrapped switch DB conducting is for bootstrap capacitor CB provides from input IN to the charging path with reference to ground GND.As low side switch M _LSDuring shutoff, bootstrapped switch DB turn-offs, to guarantee the fail safe of bootstrap capacitor CB charging path.In the illustrative examples such as Fig. 2, bootstrapped switch DB is illustrated as and comprises diode DB, yet will be understood by those skilled in the art that the implementation of bootstrapped switch DB is not limited to diode, and bootstrapped switch DB can also comprise MOSFET, JFET, the gate-controlled switch devices such as BJT.In this case, can provide switch controlling signal for bootstrapped switch DB by control circuit 103, to drive itself and low side switch M _LSSynchronously conducting and shutoff.

According to an embodiment of the present utility model, boostrap circuit 102 can also comprise bootstrapping power supply adjustment module BSTREG, couple input IN and bootstrap capacitor CB, be used for that input voltage vin is adjusted into suitable bootstrapping charging voltage VB and think bootstrap capacitor CB charging.Like this, give the bootstrap capacitor CB bootstrap voltage mode V that charging obtains _BSTMaximum can be limited at bootstrapping charging voltage VB.For example: if input voltage vin is 12V, wish to obtain the bootstrap voltage mode V of 5V _BST, then can the bootstrapping charging voltage that the input voltage vin of 12V is adjusted into 5V be thought bootstrap capacitor CB charging by bootstrapping power supply adjustment module BSTREG.According to an embodiment of the present utility model, bootstrapping power supply adjustment module BSTREG comprises low difference voltage regulator.

According to an embodiment of the present utility model, control circuit 103 can comprise the first comparison module 104, this first comparison module 104 has the first input, second input and first output relatively relatively relatively, and this first relatively input receive bootstrap voltage mode V _BST, receive bootstrap voltage mode at this second comparison input and refresh threshold value Vth1, and with bootstrap voltage mode V _BSTRefresh threshold value Vth1 (first threshold voltage Vth1) with bootstrap voltage mode and compare, thereby provide described bootstrap voltage mode refresh signal RFS at this first comparison output.If bootstrap voltage mode V _BSTBe lower than bootstrap voltage mode and refresh threshold value Vth1, then bootstrap voltage mode refresh signal RFS has the first logic state (such as the high level logic state).If bootstrap voltage mode V _BSTBe higher than bootstrap voltage mode and refresh threshold value Vth1, then bootstrap voltage mode refresh signal RFS has the second logic state (such as the low-level logic state).

According to an embodiment of the present utility model, bootstrap voltage mode refreshes threshold value Vth1 (first threshold Vth1) can comprise that first refreshes threshold value Vth1 _LWith second refresh threshold value Vth1 _H, wherein said first refreshes threshold value Vth1 _LRefresh threshold value Vth1 less than described second _HIf bootstrap voltage mode V _BSTBe lower than first and refresh threshold value Vth1 _L, then bootstrap voltage mode refresh signal RFS has the first logic state (such as the high level logic state).If bootstrap voltage mode V _BSTBe higher than second and refresh threshold value Vth1 _H, then bootstrap voltage mode refresh signal RFS has the second logic state (such as the low-level logic state).Refresh threshold value Vth1 first like this _LWith second refresh threshold value Vth1 _HBetween have certain sluggishness, can avoid because bootstrap voltage mode V _BSTMinor fluctuations and cause false triggering.

According to an embodiment of the present utility model, control circuit 103 can also comprise control module 105, has the first control input end, is used for receiving bootstrap voltage mode refresh signal RFS, and this control module 105 is based on bootstrap voltage mode refresh signal RFS control high-side switch M _HSWith low side switch M _LSConducting with turn-off to switch, thereby the charging of control bootstrap capacitor CB.

According to an embodiment of the present utility model, this control module 105 also has the second control input end and the 3rd control input end, wherein said the second control input end is for detection of output voltage V o, and described the 3rd control input end is for detection of the output current Io of the load condition that characterizes output OUT.This control module 105 provides high-side switch control signal SH and low side switch control signal SL based on bootstrap voltage mode refresh signal RFS, output voltage V o and output current Io.When bootstrap voltage mode refresh signal RFS had the first logic state, the high-side switch control signal SH that control module 105 provides and low side switch control signal SL were used for control high-side switch M _HSWith low side switch M _LSFrequency complementary ground with constant carries out the turn-on and turn-off switching, makes low side switch M _LSHave suitable ON time at each switching cycle, think bootstrap capacitor CB charging.When bootstrap voltage mode refresh signal RFS had the second logic state, the high-side switch control signal SH that control module 105 provides and low side switch control signal SL were used for control high-side switch M _HSWith low side switch M _LSCarry out the turn-on and turn-off switching according to output voltage V o and output current Io.

According to an embodiment of the present utility model, control module 105 can flow through by detection the electric current I of outputting inductance Lo _LOPerhaps flow through high-side switch M _HSElectric current I _HDetect output current Io, so that the signal of the load condition that characterizes output OUT, i.e. load signal V to be provided _Load

According to an embodiment of the present utility model, control circuit 103 can also comprise driver module 106, receives bootstrap voltage mode V _BST, high-side switch control signal SH and low side switch control signal SL, and based on bootstrap voltage mode V _BSTProvide the high-side switch of enhancing to drive signal DR with high-side switch control signal SH _H, be used for driving high-side switch M _HSTurn-on and turn-off, simultaneously, provide the low side switch of enhancing to drive signal DR based on low side switch control signal SL _L, be used for driving low side switch M _LSTurn-on and turn-off.

According to an embodiment of the present utility model, driver module 106 can comprise high-side switch driver 106 _HWith low side switch driver 106 _LHigh-side switch driver 106 _HReceive bootstrap voltage mode V _BSTWith high-side switch control signal SH, and based on bootstrap voltage mode V _BSTProvide the high-side switch of enhancing to drive signal DR with high-side switch control signal SH _H, be used for driving high-side switch M _HSTurn-on and turn-off.Downside low side switch driver 106 _LReceive low side switch control signal SL, and provide the low side switch of enhancing to drive signal DR based on low side switch control signal SL _L, be used for driving low side switch M _LSTurn-on and turn-off.According to an embodiment of the present utility model, described high-side switch driver 106 _HCan comprise one or more inverters, described bootstrap voltage mode V _BSTPower supply as described one or more inverters.Similarly, described low side switch drives 106 _LAlso can comprise one or more inverters.

According to an embodiment of the present utility model, control circuit 103 can also comprise the under-voltage block of valve circuit 107 of bootstrapping, has the first block of valve input, the second block of valve input and block of valve output.This first block of valve input is used for receiving bootstrap voltage mode V _BST, this second block of valve input is used for receiving bootstrapping under-voltage threshold value Vth2 (Second Threshold voltage Vth2).Described bootstrapping is under-voltage, and block of valve circuit is used for bootstrap voltage mode V _BSTUnder-voltage threshold value Vth2 compares with bootstrap voltage mode, and provides bootstrapping under-voltage signal LOCK at described block of valve output.If bootstrap voltage mode V _BSTBe lower than the under-voltage threshold value Vth2 of bootstrap voltage mode, the under-voltage signal LOCK that then boots has the first logic state (such as the high level logic state).At this moment control circuit 103 is controlled high-side switch M _HSWith low side switch M _LSTurn-off, stop conducting and turn-off switching.If bootstrap voltage mode V _BSTBe higher than the under-voltage threshold value Vth2 of bootstrap voltage mode, the under-voltage signal LOCK that then boots has the second logic state (such as the low-level logic state), and at this moment control circuit 103 allows control high-side switch M _HSWith low side switch M _LSCarrying out turn-on and turn-off switches.According to an embodiment of the present utility model, the under-voltage threshold value Vth2 of described bootstrap voltage mode refreshes threshold value Vth1 less than described bootstrap voltage mode.The under-voltage block of valve circuit 107 of booting helps at described bootstrap voltage mode V _BSTBe lower than the under-voltage threshold value Vth2 of bootstrap voltage mode, and failed in time to be refreshed that (that is, bootstrap capacitor CB fails to be made this bootstrap voltage mode V by in time charging _BSTReturn to and be higher than the under-voltage threshold value Vth2 of this bootstrap voltage mode) time, with described high-side switch M _HSWith described low side switch M _LSAll turn-off, to improve the work safety of voltage conversion circuit 100.

Fig. 3 shows the circuit framework schematic diagram according to the voltage conversion circuit 200 of an embodiment of the utility model.For the sake of simplicity and be convenient to understand, continued to use identical Reference numeral with same or similar assembly or structure identical in voltage conversion circuit 100 on those functions in the voltage conversion circuit 200.

As shown in Figure 3, according to an embodiment of the present utility model, control module 105 can comprise the second comparison module 201, has the 3rd comparison input, the 4th relatively input and the second comparison output.The described the 3rd compares input is used for receiving the load signal V that characterizes described output current Io (namely characterizing the load condition of output OUT) _Load, the described the 4th compares input is used for receiving underloading threshold value Vth3 (the 3rd threshold voltage vt h3).Described the second comparison module is used for load signal V _LoadVth3 compares with the underloading threshold value, and provides load comparison signal CMP at described the second comparison output.If load signal V _LoadBe higher than underloading threshold value Vth3, show that then voltage conversion circuit 200 is operated in non-underloading and non-Light Condition, at this moment load comparison signal CMP has the first logic state (such as the high level logic state).If load signal V _LoadBe lower than underloading threshold value Vth3, show that then voltage conversion circuit 200 is operated in underloading or Light Condition, at this moment load comparison signal CMP has the second logic state (such as the low-level logic state).

According to an embodiment of the present utility model, if load comparison signal CMP has the first logic state (that is, load signal V _LoadBe higher than underloading threshold value Vth3, the load condition of output OUT is non-underloading and zero load), then control circuit 103 is based on this load comparison signal CMP control high-side switch M _HSWith low side switch M _LSBe operated in deciding the frequency conducting and turn-offing switch mode of pulse width modulation (PWM).If load comparison signal CMP has the second logic state (that is, load signal V _LoadBe lower than underloading threshold value Vth3, the load condition of output OUT is underloading or zero load), then control circuit 103 is based on this load comparison signal CMP control high-side switch M _HSWith low side switch M _LSBe operated in the frequency conversion conducting and shutoff switch mode of pulse frequency modulated (PFM).According to an embodiment of the present utility model, if load comparison signal CMP has the first logic state, high-side switch M _HSWith low side switch M _LSBe operated in pulse width modulation (PWM) decide the frequency switch mode time, described high-side switch M _HSWith described low side switch M _LSConducting be constant the first switching frequency F substantially with turn-offing switching frequency _CIf load comparison signal CMP has the first logic state, high-side switch M _HSWith low side switch M _LSWhen being operated in the frequency conversion switch mode of pulse frequency modulated (PFM), described high-side switch M _HSWith described low side switch M _LSConducting with turn-off the second switching frequency F of switching frequency for changing _S, it is according to the load condition of output OUT, namely according to load signal V _LoadVariation and change less (for example, the load signal V of the load of output OUT _LoadLess), this second switching frequency F _SAlso less, to reduce voltage conversion circuit 200 (that is, load signal V under underloading or no-load condition _LoadWhen being lower than underloading threshold value Vth3) power consumption.

According to an embodiment of the present utility model, the second comparison module 201 also has the input of enabling and is used for receiving described bootstrap voltage mode refresh signal RFS, and this bootstrap voltage mode refresh signal RFS is used for controlling enabling and not enabling of described the second comparison module 201.When bootstrap voltage mode refresh signal RFS has the first logic state (that is, bootstrap voltage mode V _BSTBe lower than bootstrap voltage mode and refresh threshold value Vth1) time, the second comparison module 201 does not enable, and the load comparison signal CMP constant ground of its output has the first logic state.When bootstrap voltage mode refresh signal RFS has the second logic state (that is, bootstrap voltage mode V _BSTBe higher than bootstrap voltage mode and refresh threshold value Vth1) time, the second comparison module 201 enables, and the load comparison signal CMP of its output is according to the load signal V of the load condition that characterizes output OUT _LoadHave the first logic state or the second logic state with the comparative result of underloading threshold value Vth3.Like this, if bootstrap voltage mode V _BSTBe lower than bootstrap voltage mode and refresh threshold value Vth1, then bootstrap voltage mode refresh signal RFS does not enable the second comparison module 201, even load signal V _LoadBe lower than underloading threshold value Vth3 (load condition that is output OUT is underloading or zero load), the load comparison signal CMP of the second comparison module 201 outputs still has the first logic state, and control circuit 103 will be controlled high-side switch M _HSWith low side switch M _LSBe operated in deciding the frequency conducting and turn-offing switch mode, high-side switch M of pulse width modulation (PWM) _HSWith low side switch M _LSWith the frequency of constant (described first frequency F for example _C) periodically, complementally carry out the turn-on and turn-off switching, make low side switch M _LSHave suitable ON time at each switching cycle, think bootstrap capacitor CB charging.Until that the quantity of electric charge on the bootstrap capacitor CB is charged to is abundant, so that bootstrap voltage mode V _BSTBe refreshed to and be higher than bootstrap voltage mode and refresh threshold value Vth1, then bootstrap voltage mode refresh signal RFS enables the second comparison module 201, and control circuit 103 is according to load signal V _LoadComparative result (being load comparison signal CMP) control high-side switch M with underloading threshold value Vth3 _HSWith low side switch M _LSWhat be operated in the frequency conversion switch mode of pulse frequency modulated (PFM) or pulse width modulation (PWM) decides the frequency switch mode.

According to an exemplary embodiment of the present utility model, when bootstrap voltage mode refresh signal RFS has the first logic state, its control underloading threshold value Vth3 (for example reduces, control underloading threshold value Vth3 is coupled to reference to ground GND), so that the second comparison module 201 does not enable, make the load comparison signal CMP constant ground of the second comparison module 201 outputs have the first logic state.When bootstrap voltage mode refresh signal RFS had the second logic state, its control underloading threshold value Vth3 restored, so that the second comparison module 201 enables, made the load comparison signal CMP of the second comparison module 201 outputs according to load signal V _LoadHave the first logic state or the second logic state with the comparative result of underloading threshold value Vth3.

According to an embodiment of the present utility model, control module 105 can also comprise pulse width modulation module 202, has the first modulation input, the second modulation input, the 3rd modulation input and modulation output, wherein said the first modulation input is used for receiving described load comparison signal CMP, described the second modulation input is for detection of output voltage V o, described the 3rd modulation input is for detection of output current Io, and described modulation output provides high-side switch control signal SH and the low side switch control signal SL of pulse width modulation based on described output voltage V o and described output current Io.

According to an embodiment of the present utility model, pulse width modulation module 202 is also regulated high-side switch control signal SH and the low side switch control signal SL of described pulse width modulation according to load comparison signal CMP, when load comparison signal CMP has the first logic state (that is, load signal V _LoadBe higher than underloading threshold value Vth3) time, high-side switch control signal SH and low side switch control signal SL keep pulse width modulation or are converted to pulse width modulation by pulse frequency modulated, so that high-side switch M _HSWith low side switch M _LSCarry out deciding the frequency conducting and turn-offing switching of pulse width modulation.When load comparison signal CMP has the second logic state (that is, load signal V _LoadBe lower than underloading threshold value Vth3) time, high-side switch control signal SH and low side switch control signal SL are converted to pulse frequency modulated by pulse width modulation, so that high-side switch M _HSWith low side switch M _LSThe frequency conversion conducting of carrying out pulse frequency modulated is switched with shutoff.

According to an embodiment of the present utility model, when load comparison signal CMP has the first logic state (that is, load signal V _LoadBe higher than underloading threshold value Vth3) time, pulse width modulation module 202 makes high-side switch control signal SH and low side switch control signal SL control high-side switch M _HSWith low side switch M _LSKeep/recover the frequency turn-on and turn-off of deciding of pulse width modulation to switch.When load comparison signal CMP has the second logic state (that is, load signal V _LoadBe lower than underloading threshold value Vth3) time, pulse width modulation module 202 makes high-side switch control signal SH and low side switch control signal SL control high-side switch M _HSWith low side switch M _LSTurn-off, stop turn-on and turn-off and switch.Like this, pulse width modulation module 202 has just realized making high-side switch control signal SH and the conversion of low side switch control signal SL between pulse width modulation and pulse frequency modulated according to load comparison signal CMP, and then has realized control high-side switch M _HSWith low side switch M _LSDeciding the frequency conducting and turn-offing the frequency conversion conducting of switching and pulse frequency modulated and the conversion between the shutoff switching in pulse width modulation.

According to an embodiment of the present utility model, pulse width modulation module 202 can comprise pulse width modulating signal circuit for generating 203, switching frequency control circuit 204 and logic control circuit 205.Pulse width modulating signal circuit for generating 203 receives the first feedback signal V that characterizes output voltage V o _FBWith the second feedback signal Vcs1 of the load current that characterizes output OUT, and based on the first feedback signal V _FBProvide pulse width modulating signal C with the second feedback signal Vcs1 _PWMSwitching frequency control circuit 204 receives the load comparison signal CMP by 201 outputs of the second comparison module, and provide switching frequency modulation signal Clk based on this load comparison signal CMP, when load comparison signal CMP had the first logic state, switching frequency modulation signal Clk had the first switching frequency F of constant _C, when load comparison signal CMP had the second logic state, switching frequency modulation signal Clk had the load signal V with the load condition that characterizes output OUT _LoadThe the second switching frequency F that changes _SLogic control circuit 205 received pulse bandwidth modulation signals C _PWMWith switching frequency modulation signal Clk, and based on described pulse width modulating signal C _PWMProvide high-side switch control signal SH and low side switch control signal SL with switching frequency modulation signal Clk.When load comparison signal CMP had the first logic state, high-side switch control signal SH and low side switch control signal SL were the first switching frequency F with constant _CPulse width modulating signal, be used for control high-side switch M _HSWith low side switch M _LSCarry out deciding the frequency conducting and turn-offing switching of pulse width modulation.When load comparison signal CMP had the second logic state, high-side switch control signal SH and low side switch control signal SL had load condition with output OUT (namely with load signal V _Load) the second switching frequency F of changing _SPulse frequency modulated signal, be used for control high-side switch M _HSWith low side switch M _LSThe frequency conversion conducting of carrying out pulse frequency modulated is switched with shutoff.

According to an exemplary embodiment of the present utility model, pulse width modulating signal circuit for generating 203 can comprise error amplifier 206 and pwm comparator 207, wherein, the first input end of error amplifier 206 ("-" end of for example, illustrating among Fig. 3) receives the first feedback signal V that characterizes output voltage V o _FB, its second input (for example, "+" end of illustrating among Fig. 3) receives the reference voltage V ref of the desired value that characterizes output voltage V o, and its output is used for providing the difference amplifying signal Ve that characterizes difference between output voltage V o and its desired value; The first input end of pwm comparator 207 (for example, "-" end of illustrating among Fig. 3) receives described difference amplifying signal Ve, its second input (for example, "+" end of illustrating among Fig. 3) reception characterizes the second feedback signal Vcs1 of the load current Io of output OUT, and its output is used for providing pulse width modulating signal C _PWM

According to an exemplary embodiment of the present utility model, control circuit 103 flows through high-side switch M by detection _HSElectric current I _HObtain the second feedback signal Vcs1 of the load current Io of sign output OUT.According to an exemplary embodiment of the present utility model, control circuit 103 can also comprise high-side switch current detection circuit 208, for detection of flowing through high-side switch M _HSElectric current I _HAnd provide described the second feedback signal Vcs1.

According to an exemplary embodiment of the present utility model, the load signal V of the load condition of described sign output OUT _LoadCan comprise described difference amplifying signal Ve.

According to an exemplary embodiment of the present utility model, switching frequency control circuit 204 can comprise oscillator OSC and logical circuit LOGIC, as shown in Figure 4.Oscillator OSC is for generation of the clock signal C LOCK of frequency constant, and according to an embodiment of the present utility model, the frequency of clock signal C LOCK is described second frequency F _CLogical circuit LOGIC has the first logic input terminal, the second logic input terminal and logic output terminal, this first logic input terminal is used for receiving described clock signal C LOCK, this second logic input terminal is used for receiving described load comparison signal CMP, and this logical circuit provides described switching frequency modulation signal Clk based on described clock signal C LOCK and described load comparison signal CMP.When described load comparison signal has the first logic state (for example high level logic state), described logical circuit LOGIC exports described clock signal C LOCK as switching frequency modulation signal Clk, when described load comparison signal has the second logic state (for example low-level logic state), the switching frequency modulation signal Clk of described logical circuit LOGIC output is the low-level logic state, that is to say at this moment described clock signal C LOCK conductively-closed (described logical circuit LOGIC has skipped a part of pulse of described clock signal C LOCK).In the exemplary embodiment of Fig. 4 signal, logical circuit LOGIC comprises and circuit.

Still with reference to shown in Figure 3, according to an embodiment of the present utility model, control circuit 103 can also comprise zero passage detection module 209 to the below, and its first input end ("+" end of for example, illustrating among Fig. 3) receives to characterize and flows through low side switch M _LSElectric current I _LThe 3rd feedback signal Vcs2, its second input (for example, "-" end of illustrating among Fig. 3) receive low side switch current limit threshold Vth4 (the 4th threshold voltage vt h4), its output provides zero passage comparison signal C according to the comparative result of the 3rd feedback signal Vcs2 and low side switch current limit threshold Vth4 _ZCDWhen the 3rd feedback signal Vcs2 is higher than low side switch current limit threshold Vth4, zero passage comparison signal C _ZCD(for example: the high level logic state), control circuit 103 is based on this zero passage comparison signal C to have the first logic state _ZCDAllow low side switch M _LSCarrying out turn-on and turn-off switches.When the 3rd feedback signal Vcs2 is lower than low side switch current limit threshold Vth4, zero passage comparison signal C _ZCD(for example: the low-level logic state), control circuit 103 is based on this zero passage comparison signal C to have the second logic state _ZCDWith low side switch M _LSTurn-off, make it stop turn-on and turn-off and switch.

According to an embodiment of the present utility model, described control circuit 103 passes through described zero passage comparison signal C _ZCDBe coupled to described low side switch driver 106 _LRealize according to described zero passage comparison signal C _ZCDTo described low side switch M _LSControl.For example, according to an embodiment of the present utility model, described low side switch driver 106 _LHave the input of enabling, be used for receiving described zero passage comparison signal C _ZCDAs described zero passage comparison signal C _ZCDWhen having the first logic state, this low side switch driver 106 _LEnable and drive low side switch M _LSCarrying out turn-on and turn-off switches.As described zero passage comparison signal C _ZCDWhen having the second logic state, this low side switch driver 106 _LDo not enable, with low side switch M _LSTurn-off, make it stop turn-on and turn-off and switch.

According to an embodiment of the present utility model, low side switch current limit threshold Vth4 is zero, in order to (flow through low side switch M when the 3rd feedback signal Vcs2 is lower than zero _LSElectric current I _LWhen being lower than zero) with low side switch M _LSTurn-off, thereby reduce low side switch M _LSConduction loss and handoff loss, improve the conversion efficiency of voltage conversion circuit 200.

According to an embodiment of the present utility model, what low side switch current limit threshold Vth4 can have a setting is lower than zero and close to zero offset V _OS, this offset V _OSAmplitude smaller, can select suitable value according to actual design and application demand.For example, offset V _OSCan be with reference to the electric current I that was operated in ultralight year or flows through when unloaded high-side switch at voltage conversion circuit 200 _HThe minimum peak that needs to keep is selected.Low side switch current limit threshold Vth4 is set as is lower than zero and close to zero offset V _OS, mean to allow to flow through low side switch M _LSElectric current I _LLess than zero but close to zero.Help like this when voltage conversion circuit 200 is operated in ultralight year or is unloaded, still can guarantee to flow through high-side switch M _HSElectric current I _HGreater than zero, be used for flowing through low side switch M _LSElectric current I _LMinus part compensate.In this case, has the first logic state (that is, bootstrap voltage mode V as bootstrap voltage mode refresh signal RFS _BSTBe lower than bootstrap voltage mode and refresh threshold value Vth1) time, if voltage conversion circuit 200 is operated in underloading or Light Condition (that is, load comparison signal CMP has the first logic state), so with first frequency F _CCarry out the conducting and the high-side switch M that turn-offs complementary switching of pulse width modulation _HSWith low side switch M _LSCan have relatively large ON time, thereby make bootstrap capacitor CB in a switching cycle, have the suitable charging interval, so that as early as possible with bootstrap voltage mode V _BSTFlush to and be higher than at least bootstrap voltage mode and refresh threshold value Vth1, guarantee high-side switch M _HSNormally with turn-off to switch, thereby strengthen the job stability of voltage conversion circuit 200.Simultaneously, because offset V _OSBe lower than zero and close to zero, its amplitude is smaller, thereby allows to flow through low side switch M _LSElectric current I _LIt is very little to be lower than zero part, can obviously not increase low side switch M _LSConduction loss and handoff loss, can not cause negative influence to the conversion efficiency of voltage conversion circuit 200 yet.

Fig. 5 shows the groundwork waveform schematic diagram according to the as shown in Figure 3 voltage conversion circuit 200 of an embodiment of the utility model.Next in connection with Fig. 3 and Fig. 5 voltage conversion circuit 200 is further explained.In the exemplary signal of Fig. 5, control circuit 103 flows through high-side switch M by detection _HSElectric current I _HTo obtain to characterize described the second feedback signal Vcs1 of load current Io, the load signal V of the load condition of described sign output OUT _LoadComprise described difference amplifying signal Ve.Because difference amplifying signal Ve defines and flows through high-side switch M _HSElectric current I _HPeak value, thereby difference amplifying signal Ve can be used as characterizing the load signal V of output load condition _LoadCertainly, select difference amplifying signal Ve as load signal V _LoadJust according to a kind of illustrative embodiments of the present utility model, will be understood by those skilled in the art that, according to different embodiment of the present utility model, load signal V _LoadCan also select other suitable signal, such as load current Io, outputting inductance electric current I _L, high-side switch M _HSElectric current I _H, perhaps their peak value, mean value, and sampled signal, etc.As shown in Figure 5, load current Io is at t ₀To t ₃Lower in time, can think that the load of output OUT is lighter, at t ₃Moment back loading electric current I _oIncrease, can think that the load of output OUT becomes heavier suddenly.

At t ₀To t ₁Constantly, bootstrap voltage mode V _BSTBe higher than first and refresh threshold value Vth1 _LThen the bootstrap voltage mode refresh signal RFS of the first comparison module 104 outputs has the second logic state (being illustrated as the low-level logic state among Fig. 5), this moment, the second comparison module 201 enabled, the logic state of the load comparison signal CMP of its output depends on the comparative result of load signal Ve and underloading threshold value Vth3, and control circuit 103 is according to load comparison signal CMP control high-side switch M _HSWith low side switch M _LSBe operated in the frequency conversion switch mode of pulse frequency modulated.Particularly, in conjunction with the utility model exemplary embodiment as shown in Figure 3 and Figure 4, when load signal Ve is higher than underloading threshold value Vth3, load comparison signal CMP has the first logic state (being illustrated as the high level logic state among Fig. 5), the clock signal C LOCK that oscillator OSC produces (can think as frequency switch-over control signal Clk, this moment, frequency switch-over control signal Clk copied the partial pulse of clock signal C LOCK, had the first switching frequency F of constant _C).When load signal Ve is lower than underloading threshold value Vth3, load comparison signal CMP has the second logic state (being illustrated as the low-level logic state among Fig. 5), frequency switch-over control signal Clk is low level (can think that this moment, frequency switch-over control signal Clk skipped the partial pulse of clock signal C LOCK).Therefore, switching frequency modulation signal Clk has the second switching frequency F that changes with load signal Ve _SThereby control module 105 is based on this switching frequency control signal Clk control high-side switch M _HSWith low side switch M _LSBe operated in the frequency conversion switch mode of pulse frequency modulated.At t ₁Constantly, bootstrap voltage mode V _BSTDrop to and be lower than first and refresh threshold value Vth1 _LThe bootstrap voltage mode refresh signal RFS saltus step of the first comparison module 104 outputs is for having the first logic state (being to think the high level logic state among Fig. 5), bootstrap voltage mode refresh signal RFS controls the second comparison module 201 and does not enable (be illustrated as among Fig. 5 by underloading threshold value Vth3 being reduced to be coupled to reference to ground GND and realize) at this moment, then load comparison signal CMP constant ground has the first logic state (being illustrated as the high level logic state among Fig. 5), can think that frequency switch-over control signal Clk has copied again a part of pulse of clock signal C LOCK, has the first switching frequency F this moment _CControl module 105 is controlled high-side switch M so _HSWith low side switch M _LSWith this first switching frequency F _CComplementally carry out turn-on and turn-off and switch, at the low side switch M of each switching cycle _LSON time in charge for bootstrap capacitor CB.Through several switching cycles, until t ₂Constantly, bootstrap voltage mode V _BSTBe charged to and be higher than second and refresh threshold value Vth1 _H, then bootstrap voltage mode refresh signal RFS returns to and has the second logic state (being illustrated as the low-level logic state among Fig. 5), makes the second comparison module 201 recover to enable.At t ₂To t ₃Constantly, bootstrap voltage mode V _BSTContinue to be higher than first and refresh threshold value Vth1 _L, the course of work of voltage conversion circuit 200 and t ₀To t ₁Constantly identical, control circuit 103 is according to load comparison signal CMP control high-side switch M _HSWith low side switch M _LSBe operated in the frequency conversion switch mode of pulse frequency modulated.At t ₃Constantly, output current Io increases suddenly (load of output OUT increases the weight of), the load signal Ve that characterizes this output current Io continues to be higher than underloading threshold value Vth3, thereby load comparison signal CMP has the first logic state (being illustrated as the high level logic state among Fig. 5), frequency switch-over control signal Clk has copied a part of pulse of clock signal C LOCK, has the first switching frequency F of constant _CControl module 105 is controlled high-side switch M so _HSWith low side switch M _LSWith this first switching frequency F _CCarry out deciding the frequency conducting and turn-offing switching of pulse frequency modulated, at the low side switch M of each switching cycle _LSON time, bootstrap capacitor CB charging, bootstrap voltage mode V _BSTIncrease gradually, until be stabilized in bootstrapping charging voltage VB (adjustment by bootstrapping power supply adjustment module BSTREG realizes).

Based on described each exemplary embodiment of Fig. 3 to Fig. 5 and distortion execution mode thereof, control circuit 103 is based on bootstrap voltage mode V according to the utility model _BSTBy control high-side switch M _HSWith low side switch M _LSTurn-on and turn-off switch to control the charging of bootstrap capacitor CB so that at bootstrap voltage mode V _BSTWhen not enough (, at bootstrap voltage mode V _BSTWhen being lower than bootstrap voltage mode and refreshing threshold value Vth1), with bootstrap voltage mode V _BSTIn time brush is to enough (that is, making bootstrap voltage mode V greatly _BSTRefresh to being higher than bootstrap voltage mode and refresh threshold value Vth1), thus high-side switch M guaranteed _HSNormally with turn-off to drive, make voltage conversion circuit 200 normal operations.

Based on described each exemplary embodiment of Fig. 3 to Fig. 5 and distortion execution mode thereof, the first comparison module 104 is with bootstrap voltage mode V according to the utility model _BSTRefresh threshold value Vth1 with bootstrap voltage mode and compare bootstrap voltage mode refresh signal RFS is provided, to control enabling and not enabling of the second comparison module 201; If the second comparison module 201 enables, then hour (that is, characterize the load signal V of output current Io at load current Io _LoadWhen being lower than underloading threshold value Vth3, the load of output OUT is lighter), control circuit 103 will be controlled high-side switch M _HSWith low side switch M _LSBe operated in the frequency conversion switch mode of pulse frequency modulated, when load current Io is larger (, the load signal V of sign output current Io _LoadWhen being higher than underloading threshold value Vth3, the load of output OUT is heavier), control circuit 103 will be controlled high-side switch M _HSWith low side switch M _LSWhat be operated in pulse width modulation decides the frequency switch mode; If the second comparison module 201 does not enable, then regardless of the state (load condition of output OUT) of load current Io, control circuit 103 all makes high-side switch M _HSWith low side switch M _LSWhat be operated in pulse width modulation decides the frequency switch mode, thinks bootstrap capacitor CB charging.Therefore, at bootstrap voltage mode V _BSTWhen being lower than bootstrap voltage mode and refreshing threshold value Vth1 (, bootstrap voltage mode V _BSTWhen not enough), control circuit 103 does not enable the second comparison module by bootstrap voltage mode refresh signal RFS, so that high-side switch M _HSWith low side switch M _LSCarry out deciding the frequency conducting and turn-offing switching of pulse width modulation, thereby make bootstrap capacitor CB at the low side switch M of each switching cycle _LSON time in the charging, to refresh bootstrap voltage mode V _BST

Based on described each exemplary embodiment of Fig. 3 to Fig. 5 and distortion execution mode thereof, (that is, load current Io is less, characterizes the load signal V of output current Io even the load of output OUT is light according to the utility model _LoadBe lower than underloading threshold value Vth3), high-side switch M _HSWith low side switch M _LS(t shown in Figure 5 for example in the time of should being operated in the frequency conversion switch mode of pulse frequency modulated ₀To t ₃Constantly), in case bootstrap voltage mode V _BSTBe lower than bootstrap voltage mode and refresh threshold value Vth1 (t shown in Figure 5 for example ₁Constantly), then control circuit 103 makes high-side switch M _HSWith low side switch M _LSThe frequency conducting of deciding that recovers pulse width modulation is switched with turn-offing, (the t shown in Figure 5 for example so that bootstrap capacitor CB charging ₁To t ₂Constantly), bootstrap voltage mode V _BSTBegin to recover.At t ₁To t ₂Constantly, because the electric current I of high-side switch _HPeak current less, the voltage ripple of output voltage V o is less also, and the conversion efficiency of voltage conversion circuit is still higher.High-side switch M _HSWith low side switch M _LSThe frequency conducting of deciding of the small leak current pulse width modulation in process some cycles is switched with shutoff, until bootstrap voltage mode V _BSTReturn to and be higher than bootstrap voltage mode and refresh threshold value Vth1 (t shown in Figure 5 for example ₂Constantly), control circuit 103 makes high-side switch M _HSWith low side switch M _LSThe frequency conversion conducting of the pulse frequency modulated that continuation should be carried out is switched with shutoff.Voltage conversion circuit according to each exemplary embodiment of the utility model and distortion execution mode thereof can be operated in the approaching situation of output voltage V o and output voltage V in like this, and control circuit 103 not only can make bootstrap voltage mode V _BSTCan in time return to enough driving high-side switch M _HSLevel, and can not cause output voltage V o than great fluctuation process, can also guarantee that voltage conversion circuit has higher conversion efficiency.

It comprises that the beneficial effect of the voltage conversion circuit of bootstrap voltage mode refresh control circuit 103 should not be considered to only be confined to above-described according to the bootstrap voltage mode refresh control circuit 103 of each embodiment of the utility model and distortion execution mode thereof.Can be better understood by the accompanying drawing of reading detailed description of the present utility model and studying each embodiment according to these and other beneficial effect of each embodiment of the utility model.

Although in this specification as an example of the voltage-dropping type voltage conversion circuit example to illustrating according to the bootstrap voltage mode refresh control circuit of each embodiment of the utility model and the voltage conversion circuit that comprises this bootstrap voltage mode refresh control circuit and describing, but this does not also mean that restriction of the present utility model, it should be appreciated by those skilled in the art that structure given here and principle also go for having the voltage conversion circuit of other topological structure, for example: booster type voltage conversion circuit, buck-boost type voltage conversion circuit etc.

Therefore, above-mentioned specification of the present utility model and execution mode only are illustrated the bootstrap voltage mode refresh control circuit of the utility model embodiment and the voltage conversion circuit that comprises this bootstrap voltage mode refresh control circuit in an exemplary fashion, and are not used in the scope of the present utility model that limits.It all is possible changing and revise for disclosed embodiment, the selectivity embodiment that other are feasible and can be understood by those skilled in the art the equivalent variations of element among the embodiment.Other variations of embodiment disclosed in the utility model and modification do not exceed spirit of the present utility model and protection range.

Claims

1. bootstrap voltage mode refresh control circuit, be used for voltage conversion circuit, wherein said voltage conversion circuit comprises high-side switch and low side switch and is used to described high-side switch that the bootstrap capacitor of bootstrap voltage mode is provided, described voltage conversion circuit switches based on the turn-on and turn-off of described high-side switch and low side switch provides output voltage and output current, it is characterized in that described bootstrap voltage mode refresh control circuit comprises:

The first comparison module, have the first comparison input, second relatively input and the first comparison output, wherein said first compares input is used for receiving described bootstrap voltage mode, described second relatively input be used for receiving bootstrap voltage mode and refresh threshold value, described the first comparison module is used for described bootstrap voltage mode and described bootstrap voltage mode refreshed that threshold value compares and compare output described first provides the bootstrap voltage mode refresh signal; And

Control module has the first control input end and is used for receiving described bootstrap voltage mode refresh signal, and the conducting of controlling described high-side switch and described low side switch based on described bootstrap voltage mode refresh signal is switched to control the charging of described bootstrap capacitor with shutoff.

2. according to claim 1 bootstrap voltage mode refresh control circuit is characterized in that:

Described control module also has the second control input end and the 3rd control input end, wherein said the second control input end is for detection of the output voltage of described voltage conversion circuit, and described the 3rd control input end is for detection of the output current of described voltage conversion circuit;

3. bootstrap voltage mode refresh control circuit according to claim 2 is characterized in that:

Described bootstrap voltage mode refreshes threshold value and comprises that first refreshes threshold value and second and refresh threshold value, and wherein said first refreshes threshold value refreshes threshold value less than described second;

Refresh threshold value if described bootstrap voltage mode is lower than described first, described bootstrap voltage mode refresh signal has the first logic state;

Refresh threshold value if described bootstrap voltage mode is higher than described second, described bootstrap voltage mode refresh signal has the second logic state.

4. according to claim 1 to 3 one of them described bootstrap voltage mode refresh control circuit, it is characterized in that described control module comprises:

The second comparison module, have the input of enabling, the 3rd comparison input, the 4th relatively input and the second comparison output, the wherein said input that enables is used for receiving described bootstrap voltage mode refresh signal, the described the 3rd compares the load signal that input is used for receiving the output current that characterizes described voltage conversion circuit, the described the 4th relatively input be used for receiving the underloading threshold value, described the second comparison module is used for providing the load comparison signal with described load signal with described underloading threshold value compares and compare output described second;

If described the second comparison module does not enable, described load comparison signal constant ground has described the first logic state;

5. bootstrap voltage mode refresh control circuit according to claim 4, it is characterized in that, when described load comparison signal had described the first logic state, the conducting of described high-side switch and described low side switch was the first switching frequency of constant with turn-offing switching frequency; When described load comparison signal had described the second logic state, the conducting of described high-side switch and described low side switch was the second switching frequency that changes with turn-offing switching frequency; Wherein said the second switching frequency changes according to the variation of described load signal.

6. bootstrap voltage mode refresh control circuit according to claim 4 is characterized in that described control module further comprises:

7. bootstrap voltage mode refresh control circuit according to claim 6 is characterized in that:

When described load comparison signal had the first logic state, the frequency turn-on and turn-off of deciding that described pulse width modulation module controls high-side switch and low side switch carry out pulse width modulation were switched;

When described load comparison signal had the second logic state, the described high-side switch of described pulse width modulation module controls and described low side switch turn-offed, and stopped turn-on and turn-off and switched.

8. bootstrap voltage mode refresh control circuit according to claim 6 is characterized in that, described pulse width modulation module comprises:

9. bootstrap voltage mode refresh control circuit according to claim 1 is characterized in that further comprising:

10. bootstrap voltage mode refresh control circuit according to claim 9, what it is characterized in that described low side switch current limit threshold has a setting is lower than zero and close to zero offset.

11. bootstrap voltage mode refresh control circuit according to claim 1 is characterized in that further comprising:

12. a voltage conversion circuit is characterized in that, comprising:

Input is used for receiving input voltage;

Output is used for providing output voltage and output current;

High-side switch and low side switch, coupled in series in described input with reference to ground between, and coupling of described high-side switch and described low side switch forms a switched voltage output;

Output filter circuit is coupled between described switched voltage output and the described output, is used for the switched voltage of described switched voltage output is converted into described output voltage;

Boostrap circuit comprises bootstrap capacitor, couples described input and described low side switch, so that described bootstrap capacitor charges to produce bootstrap voltage mode when described low side switch conducting; And

Control circuit, receive described bootstrap voltage mode, provide the conducting of enhancing to drive signal with shutoff based on this bootstrap voltage mode for described high-side switch, and switch to control the charging of described bootstrap capacitor based on this bootstrap voltage mode by the turn-on and turn-off of controlling described high-side switch and described low side switch.

13. voltage conversion circuit according to claim 12 is characterized in that, described control circuit comprises:

14. voltage conversion circuit according to claim 13 is characterized in that:

15. voltage conversion circuit according to claim 13 is characterized in that:

16. to 15 one of them described voltage conversion circuit, it is characterized in that described control module comprises according to claim 13:

If being lower than described bootstrap voltage mode, described bootstrap voltage mode refreshes threshold value, described bootstrap voltage mode refresh signal is controlled described the second comparison module and is not enabled, refresh threshold value if described bootstrap voltage mode is higher than described bootstrap voltage mode, described bootstrap voltage mode refresh signal is controlled described the second comparison module and is enabled; Be further characterized in that,

17. voltage conversion circuit according to claim 12 is characterized in that, further comprises:

18. voltage conversion circuit according to claim 17 is characterized in that, what described low side switch current limit threshold had a setting is lower than zero and close to zero offset.