CN100468270C - Switching voltage regulator avoiding discontinuous mode - Google Patents

Abstract

The switching circuit operates in first and second operating states. In the first operating state, the switching circuit allows a linear increase of the switching current. In the second operating state, the switching circuit allows a linear reduction of the switching current. Control circuitry is coupled to the switching circuitry such that it operates in either the first or second operating state. The setting circuit generates a threshold signal such that the control circuit ensures that the switching current increases linearly in response to the threshold signal to a current value greater than or equal to a value set by the threshold signal in the first operating state. Thereby preventing the switching current from decreasing linearly to polarity reversal in the second operating state.

Description

Avoid the changeover voltage adjuster of discontinuous mode

Technical field

The present invention is about a kind of changeover voltage adjuster, especially about a kind of changeover voltage adjuster of operating under discontinuous mode avoided, thereby improves the efficient of power transfer.

Prior art

Changeover voltage adjuster is to be used for providing under an output voltage through overregulating the needed load that outputs current to.Changeover voltage adjuster reaches by the transistorized switching duty cycle of power controlling (Duty Ratio) and converts unadjusted input voltage source to desired stable output voltage.Fig. 1 shows the circuit block diagram of the synchronous suitching type step down voltage redulator of conventional employing Current Feedback Control.As shown in the figure, side switch HS and side switch LS are coupled in series in input voltage source V _InAnd between the earth potential.One end of inductance L is coupling in the common node CN between side switch HS and side switch LS, and its other end is used to provide output voltage V then as output terminal _OutTo load R _LOutput terminal also is provided with an output capacitance C _o, be used for to output voltage V _OutCarry out Filtering Processing.Side switch HS and side switch LS are controlled by upside drive signal HD and the downside drive signal LD that switching logic circuit 10 is exported respectively.In synchronous suitching type regulator, the operation of side switch HS and side switch LS is inverting each other.Pulse signal PU with fixed frequency is to switching logic circuit 10 in oscillatory circuit 11 outputs.Switch circulation at first at each, switching logic circuit 10 makes side switch HS conducting and not conducting of side switch LS in response to pulse signal PU.As a result, input voltage source V _InProvide energy to inductance L, electric current I _LThereby linear the increase.In case inductive current I _LBe increased to by voltage feedback signal V _VfbWith reference voltage signal V _RefBetween through the error signal V of excess current slope-compensation _Err2What set goes up in limited time, and comparer 12 is triggered and becomes high level output from low level output transition.In response to the triggering of comparer 12, switching logic circuit 10 makes side switch HS become not conducting and side switch LS becomes conducting.As a result, the energy that is stored in the inductance L is discharged into load R _L, cause inductive current I _LThe linear minimizing.

Fig. 2 shows the inductive current I of the synchronous suitching type step down voltage redulator among Fig. 1 _LThe waveform sequential chart.As shown in the figure, curve 21 representative inductive current I in the operation of continuous mode (Continuous Mode) _LWaveform.At each switching cycle T _SIn, inductive current I _LVariation be rendered as triangular wave, its linear rising part is in conducting state and makes input voltage source V corresponding to side switch HS _InProvide energy to inductance L, its linear sloping portion then is in not on-state and makes the energy that is stored in the inductance L be discharged into load R corresponding to side switch HS _LThe mean value I of curve 21 _Ave1Promptly be provided to load R by output-stage circuit _LElectric current.

Curve 22 representative inductive current I in the operation of discontinuous mode (Discontinuous Mode) _LWaveform.At time t1, one switches the circulation beginning, so side switch HS conducting makes inductive current I _LThe linear rising.At time t2, as inductive current I _LRise to by error signal V through slope-compensation _Err2The peak I that sets _Peak2The time, side switch HS promptly becomes not conducting, causes inductive current I _LBegin linear the minimizing subsequently.At time t3, inductive current I _LBe reduced to zero, yet nextly switched circulation and still must wait for to time t4 and could begin.In the case, inductive current I _LThe phenomenon of reversal of poles will take place in time t3 and t4 interval, also be inductive current I _LFlow direction the transformations of 180 degree take place.Therefore, conventional synchronous suitching type step down voltage redulator must additionally be provided with a current reversal circuit for detecting 17, as shown in Figure 1, makes as inductive current I _LImmediate command switching logic circuit 10 makes side switch LS become not conducting when being reduced to zero, thereby prevents inductive current I _LThe reversal of poles phenomenon takes place and reduce whole supply of electrical energy efficient.

Even be provided with current reversal circuit for detecting 17 or even use asynchronous (Non-synchronous) changeover voltage adjuster (that is to say that the combination of using power transistor and free-wheel diode is as commutation circuit) instead, can effectively prevent inductive current I _LThe reversal of poles phenomenon takes place.Yet, as shown in Figure 2, inductive current I in discontinuous mode _LIn time t3 and t4 interval, maintain zero.In the case, output voltage V _OutTake place continuation to shake up and down unavoidablely and form high frequency noise.

Summary of the invention

Because foregoing problems, one object of the present invention is to provide a kind of changeover voltage adjuster, can be adjusted under continuous mode to operate, thereby avoid the caused various shortcomings of discontinuous mode.

The inventor observes at each switches in the circulation, and when half of the peak point current of the inductance of flowing through just equaled to flow through the average value current of inductance, changeover voltage adjuster was operated under the critical operation state between continuous mode and discontinuous mode.The peak point current of inductance of flowing through this moment can be described as the threshold peak electric current (Threshold Peak Current) of continuous mode.Therefore, changeover voltage adjuster according to the present invention is provided with a threshold peak current setting circuit, is used for producing the threshold peak current signal, and it represents the threshold peak electric current of continuous mode.When the peak point current of the inductance of flowing through during,, therefore need not adjust the electric current of the inductance of flowing through owing in continuous mode, operate greater than the threshold peak electric current.Yet, when the peak point current of the inductance of flowing through is detected less than the threshold peak electric current, operate in discontinuous mode in order to prevent voltage regulator, therefore the electric current that improves the inductance of flowing through makes its peak point current still equal the threshold peak electric current in fact, thereby guarantees that changeover voltage adjuster continues to operate under continuous mode.

According to one embodiment of present invention, provide a kind of changeover voltage adjuster, comprise a commutation circuit, a control circuit and an initialization circuit.Described commutation circuit is operated under first mode of operation and second mode of operation.In first mode of operation, commutation circuit allows the linear increase of a switch current.In second mode of operation, commutation circuit allows the linear minimizing of this switch current.Control circuit is coupled to commutation circuit, is used for controlling commutation circuit and operates under first or second mode of operation.Initialization circuit produces a minimum detectable signal, make control circuit guarantee that in response to minimum detectable signal switch current increases to more than or equal to a current value that is set by minimum detectable signal at the first mode of operation neutral line, thereby prevent that switch current is reduced to reversal of poles at the second mode of operation neutral line.

According to another embodiment of the invention, provide a kind of control method of changeover voltage adjuster, comprise the following step.Control a commutation circuit and under one first mode of operation, operate, be used for allowing the linear increase of a switch current.Control this commutation circuit and under one second mode of operation, operate, be used for allowing the linear minimizing of this switch current.In the described step that this commutation circuit of control is operated under this first mode of operation, guarantee that this switch current linearity increases to more than or equal to a critical current, thereby in this step that this commutation circuit of control is operated, prevent that described electric current linearity is reduced to reversal of poles under this second mode of operation.

The accompanying drawing summary

Fig. 1 shows the circuit block diagram of the synchronous suitching type step down voltage redulator of conventional employing Current Feedback Control;

Fig. 2 shows the waveform sequential chart of the inductive current of continuous mode and discontinuous mode;

Fig. 3 shows the waveform sequential chart of the inductive current of critical operation state;

Fig. 4 shows the circuit block diagram of avoiding the synchronous suitching type step down voltage redulator of discontinuous mode according to of the present invention;

Fig. 5 shows the detailed circuit diagram according to first example of threshold peak current setting circuit of the present invention;

Fig. 6 shows the detailed circuit diagram according to second example of threshold peak current setting circuit of the present invention;

Fig. 7 shows the circuit block diagram of avoiding the synchronous suitching type boost pressure controller of discontinuous mode according to of the present invention.

Embodiment

Explanation hereinafter and accompanying drawing will make aforementioned and other purposes of the present invention, feature, more obvious with advantage.Describe in detail according to a preferred embodiment of the invention below with reference to accompanying drawings.

Peak point current and the relativeness between average value current that the inventor examines the inductance of finding behind Fig. 2 to flow through have marked difference in continuous mode with in the discontinuous mode.Particularly, in continuous mode, for example operation of curve 21 representatives, the average value current I of the inductance L of flowing through _Ave1Peak point current I greater than the inductance L of flowing through _Peak1Half.Yet, in discontinuous mode, for example operation of curve 22 representatives, the average value current I of the inductance L of flowing through _Ave2Peak point current I less than the inductance L of flowing through _Peak2Half, this is because at each switching cycle T _SIn some time internal inductance electric current I _LBe essentially zero (under the situation that is provided with the anti-locking apparatus of current reversal).Therefore, if operate under discontinuous mode for fear of changeover voltage adjuster, half of the peak point current of the inductance of then must guaranteeing to flow through is less than or equal to the average value current of the inductance of flowing through.As shown in Figure 3, curve 30 representative inductive current I in the critical operation state _LWaveform, inductive current I before each switches loop ends _LJust be reduced to zero.Critical operation state when half of peak point current of now calculating the inductance of flowing through just equals to flow through the average value current of inductance can be found the threshold peak electric current I _{Peak_TH}By dutycycle D, switching cycle T _S, input voltage source V _In, and the common decision of inductance L institute, shown in following equation (1):

$I_{\mathrm{peak}\_\mathrm{TH}}=\left(\frac{T_s}{L}\right)\·D\·(1-D)\·V_{\mathrm{in}}...\left(1\right)$

Because threshold peak electric current I _{Peak_TH}Represent the minimum admissible peak point current of continuous mode, as long as the peak point current of the inductance of therefore guaranteeing to flow through is more than or equal to this threshold peak electric current I _{Peak_TH}, can effectively avoid voltage regulator in discontinuous mode, to operate.

Fig. 4 shows the circuit block diagram of avoiding the synchronous suitching type step down voltage redulator of discontinuous mode according to of the present invention.As shown in the figure, side switch HS and side switch LS are coupled in series to input voltage source V _InAnd between the earth potential.One end of inductance L is coupled to the common node CN between side switch HS and side switch LS, and its other end is used to provide output voltage V then as output terminal _OutTo load R _LOutput terminal also is provided with an output capacitance C _o, be used for to output voltage V _OutCarry out Filtering Processing.Side switch HS and side switch LS are controlled by upside drive signal HD and the downside drive signal LD that switching logic circuit 40 is exported respectively.Switching logic circuit 40 has a SR latch (Latch) 41, and being used for provides upside drive signal HD and downside drive signal LD from reversed-phase output Q.In the embodiment shown in fig. 4, because side switch HS realizes and side switch LS is realized by nmos pass transistor by the PMOS transistor, so upside drive signal HD and downside drive signal LD are realized by synchronous signal.

The end S that is provided with of SR latch 41 is connected to the output terminal of phase inverter 42.The input end of phase inverter 42 is connected to oscillatory circuit 11, is used for received pulse signal PU.The replacement end R of SR latch 41 is connected to the output terminal of NAND logic gate 43.The first input end of NAND logic gate 43 is connected to the output terminal of comparer 12, is used for receiving the first compare result signal CR1.The inverting input of comparer 12 is connected to the output terminal of slope equalizer 13.Two input ends of slope equalizer 13 are connected respectively to the output terminal of oscillatory circuit 11 and error amplifier 14, are used for the relevant voltage feedback signal V that the sawtooth signal RA that exported based on oscillatory circuit 11 and error amplifier 14 exported _VfbWith reference voltage signal V _RefBetween error signal V _Err1And generation is through the error signal V of slope-compensation _Err2The inverting input of error amplifier 14 is connected to the output terminal of voltage feedback circuit 15, is used for receiving voltage feedback signal V _Vfb, the output voltage V of its representative voltage regulator _OutThe non-inverting input of error amplifier 14 is used for receiving a reference voltage signal V _RefThe non-inverting input of comparer 12 is connected to current feedback circuit 16, is used for received current feedback signal V _Ifb, it represents inductive current I _L

Second input end of NAND logic gate 43 is connected to the output terminal of comparer 44, is used for receiving the second compare result signal CR2.The inverting input of comparer 44 is connected to threshold peak current setting circuit 45, is used for receiving threshold peak setting signal V _{Peak_TH}The non-inverting input of comparer 44 is connected to current feedback circuit 16, is used for received current feedback signal V _IfbThe threshold peak setting signal V that is produced by threshold peak current setting circuit 45 _{Peak_TH}It is the threshold peak electric current I that representative is calculated according to aforesaid equation (1) _{Peak_TH}

Below with reference to the operation of Fig. 4 detailed description according to synchronous suitching type step down voltage redulator of the present invention.Oscillatory circuit 11 is produced has period T _SPulse signal PU via phase inverter 42 be provided to SR latch 41 be provided with the end S.Because SR latch 41 is negative sense trigger circuit, therefore SR latch 41 is triggered in the rising edge of pulse signal PU after anti-phase, its reversed-phase output Q is provided have low level upside drive signal HD and downside drive signal LD, begin to carry out one and switch circulation.Low level upside drive signal HD makes side switch HS conducting, and low level downside drive signal LD makes not conducting of side switch LS.As a result, input voltage source V _InProvide energy to arrive inductance L, inductive current I _LThereby linear the increase.Current feedback circuit 16 detecting inductive current I _L, and generation is used for representing inductive current I _LCurrent feedback signal V _IfbCurrent feedback signal V _IfbBe provided to comparer 12 and 44, be used for relatively passing through respectively the error signal V of slope-compensation _Err2) threshold peak setting signal V _{Peak_TH}

By means of the effect of comparer 12, in case the linear current feedback signal V that rises _IfbExceed error signal V through slope-compensation _Err2The time, the first compare result signal CR1 is transformed into high level state from low level state immediately.On the other hand, by means of the effect of comparer 44, in case the linear current feedback signal V that rises _IfbExceed threshold peak setting signal V _{Peak_TH}The time, the second compare result signal CR2 is transformed into high level state from low level state immediately.The first compare result signal CR2 and the second compare result signal CR2 control the replacement end R of SR latch 41 via the coupling of NAND logic gate 43.Therefore, the end R condition of (that is to say that the output signal of NAND logic gate 43 is transformed into low level state from high level state) of being triggered of resetting is that first and second compare result signal CR1 and CR2 must be in high level state simultaneously and could satisfy.In other words, even the linear current feedback signal V that rises _IfbBecause exceeded error signal through slope-compensation _Verr2And make the first compare result signal CR1 when low level state is transformed into high level state, if this moment current feedback signal V _IfbDo not exceed threshold peak setting signal V yet _{Peak_TH},,, can't trigger the end R that resets so the output signal of NAND logic gate 43 maintains high level state then because the second compare result signal CR2 still is in low level state.As a result, side switch HS still keeps conducting, makes current feedback signal V _IfbContinue to rise up to exceeding threshold peak setting signal V _{Peak_TH}

When the end R that resets was triggered, the reversed-phase output Q of SR latch provided upside drive signal HD and the downside drive signal LD with high level.The upside drive signal HD of high level makes not conducting of side switch HS, and the downside drive signal LD of high level makes side switch LS conducting.As a result, the energy that is stored in inductance L is discharged into load R _L, inductive current I _LThereby linear the minimizing.The peak point current of inductance must be more than or equal to the threshold peak electric current I owing to flow through _{Peak_TH}, the end R that resets is triggered, thus pulse signal PU trigger once more be provided with end S with enter next switch circulation before, inductive current I _LCan not be reduced to reversal of poles.Therefore, synchronous suitching type step down voltage redulator according to the present invention is avoided operating in discontinuous mode effectively, has solved that conventional inductive current reversal of poles and/or output voltage shake up and down and the problem that forms high frequency noise.

In the embodiment shown in fig. 4, because comparer 12 all is designed to voltage comparator circuit with comparer 44, also be that input end is used for receiving voltage signal and output terminal and is used for output voltage signal, so current feedback circuit 16 all is designed to output voltage signal V with threshold peak current setting circuit 45 _IfbWith V _{Peak_TH}, be used for representing indirectly pairing electric current physical quantity I _LWith I _{Peak_TH}, but not direct output current signal.Please note that the present invention can also be applied to the situation that current feedback circuit 16 and threshold peak current setting circuit 45 are designed to direct output current signal.For example, electric current additionally is set to electric pressure converter at the output terminal of current feedback circuit 16 and threshold peak current setting circuit 45, the current signal that is used for being exported converts voltage signal to.Another kind of feasible method then is to use the error signal V of voltage-to-current converter with voltage _Err2Convert current signal to, simultaneously comparer 12 and comparer 44 are designed to current comparison circuit.In this case, current feedback circuit 16 also is designed to direct output current signal with threshold peak current setting circuit 45.

From equation (1) as can be known, threshold peak setting signal V _{Peak_TH}Change along with the second power of dutycycle.Except steady state (SS) had been set up, dutycycle changed along with the real time operation state of voltage regulator.Even under steady state (SS), dutycycle also may be because of input voltage source V _InDescend gradually and necessary the increase so that output voltage V _OutMaintain desired desired value.Therefore, threshold peak current setting circuit 45 according to the present invention is not only to produce a fixed signal, and must be based on the real time operation state of voltage regulator and adjust needed threshold peak setting signal V _{Peak_TH}

Fig. 5 shows the detailed circuit diagram according to first example of threshold peak current setting circuit 45-1 of the present invention.As shown in the figure, in response to unadjusted output voltage V _InAnd have period T _SSawtooth signal RA, threshold peak current setting circuit 45-1 produces threshold peak setting signal V _{Peak_TH}, it is represented according to aforesaid equation (1) the threshold peak electric current I that obtains of calculating _{Peak_TH}Particularly, input voltage V _InForm threshold peak setting signal V via the linear amplification of operational amplifier OP1 and OP2 in regular turn _{Peak_TH}, can be expressed as follows formulation (2):

$V_{\mathrm{peak}\_\mathrm{TH}}=\left(\frac{R_{v1}}{R_{c1}}\right)\·\left(\frac{R_{v2}}{R_{c2}}\right)\·V_{\mathrm{in}}...\left(2\right)$

Here R _C1Be to be connected to input voltage V _InAnd the fixed resistance between the inverting input of operational amplifier OP1, R _V1Be to be connected to the inverting input of operational amplifier OP1 and the linearly variable resistance between the output terminal, R _C2Be fixed resistance and the R that is connected between the inverting input of the output terminal of operational amplifier OP1 and operational amplifier OP2 _V2Be to be connected to the inverting input of operational amplifier OP2 and the linearly variable resistance between the output terminal.

Linearly variable resistance R _V1Be designed to a function of time, can be expressed as equation (3):

R _v1(t)＝R _v1，t＝0·D(t) ...(3)

Here R _{V1, t=0}Be linearly variable resistance R _V1Initial resistance value when switching the circulation beginning, and D (t) is one and has period T _SThe function of time, it is worth from 0 linear increment to 1.Linearly variable resistance R _V2Also be designed to another function of time, can be expressed as equation (4):

R _v2(t)＝R _v2，t＝0·(1-D)(t) ...(4)

Here R _{V2, t=0}Be linearly variable resistance R _V2Initial resistance value when switching the circulation beginning, and (1-D) (t) for having period T _SThe function of time, it is worth from 1 linear decrease to 0.The amplitude of the sawtooth signal RA that oscillatory circuit 11 shown in Figure 4 is produced is along with the time linear increment and have period T _STherefore, linearly variable resistance R _V1The modulation of the sawtooth signal RA that can be produced by oscillatory circuit 11 is implemented.On the other hand, can form an anti-phase waveform behind the sawtooth signal RA process phase inverter INV, its amplitude is along with the time linear decrease and have period T _STherefore, linearly variable resistance R _V2Can implement by the modulation of this anti-phase sawtooth signal.

By with equation (3) and (4) substitution equation (2), threshold peak setting signal V _{Peak_TH}Can be expressed as follows and state equation (5):

$V_{\mathrm{peak}\_\mathrm{TH}}\left(t\right)=\left(\frac{R_{v1,t=0}}{R_{c1}}\right)\·\left(\frac{R_{v2,t=0}}{R_{c2}}\right)\·D\left(t\right)\·(1-D)\left(t\right)\·V_{\mathrm{in}}...\left(5\right)$

Compare equation (1) and (5), can find that the proportionality constant item that is made of each resistance value need be designed to satisfy following condition (6):

$\left(\frac{R_{v1,t=0}}{R_{c1}}\right)\·\left(\frac{R_{v2,t=0}}{R_{c2}}\right)=\frac{T_s}{L}...\left(6\right)$

Switch in the circulation, at each as current feedback signal V _IfbReach error signal V through slope-compensation _Err2The time, this is pairing threshold peak setting signal V constantly _{Peak_TH}Also produced by threshold peak current setting circuit 45-1 exactly.Therefore, comparer 44 can be judged current feedback signal V effectively _IfbWhether exceed threshold peak setting signal V _{Peak_TH}, under discontinuous mode, operate to avoid voltage regulator.

Fig. 6 shows the detailed circuit diagram according to second example of threshold peak current setting circuit 45-2 of the present invention.As shown in the figure, input voltage V _InVia operational amplifier OP _a, nmos pass transistor N1 and resistance R _aThe linear current regulator that is constituted and determine an electric current I _a, can be expressed as follows formulation (7):

$I_a=\left(\frac{V_{\mathrm{in}}}{R_a}\right)...\left(7\right)$

In other words, electric current I _aBe proportional to input voltage V _InPMOS transistor P1 to P4 constitutes the current mirror of a multiple output stage, and its output stage transistor P2 to P4 provide electric current I respectively _aTransistor P2 provide electric current I _aTo one that is constituted by PMOS transistor P5 and P6 differential to (Differential Pair).Transistor P3 provide electric current I _aTo constituted by PMOS transistor P7 and P8 another is differential right.The grid of transistor P5 is connected to a lower boundary reference voltage V _B1, and the grid of transistor P8 is connected to a coboundary reference voltage V _BhThe grid of transistor P6 and P7 interconnects, and is used to receive the sawtooth signal RA that oscillatory circuit 11 is produced.

The electric current I that transistor P3 is provided _aAccording to lower boundary reference voltage V _B1And the difference between sawtooth signal RA and what determine to distribute to transistor P5.In other words, by transistor P5 and P6 constituted differential to by lower boundary reference voltage V _B1RA controls with sawtooth signal, is used for according to the variation of sawtooth signal RA and from electric current I _aIn choose the one-period change component, make its transistor P5 that flows through.The electric current I that transistor P4 is supplied _aAccording to sawtooth signal RA and coboundary reference voltage V _BhBetween difference and what determine to distribute to transistor P8.In other words, by transistor P7 and P8 constituted differential to by sawtooth signal RA and coboundary reference voltage V _BhControl, be used for according to the variation of sawtooth signal RA and from electric current I _aIn choose the one-period change component, make its transistor P8 that flows through.Subsequently, the cyclical variation component addition each other of flow through transistor P5 and P8, and the current mirror that is constituted by nmos pass transistor N3 and N4 is converted to electric current I _b

Threshold peak setting signal V _{Peak_TH}Pass through electric current I _a, I _b, and I _cThe resistance R of flowing through _bThe voltage difference that is caused and implementing can be expressed as follows formulation (8):

V _{peak_TH}＝(I _a-I _b+I _c)·R _b ...(8)

Electric current I _aBe to be used for input voltage V in the simulation equation formula (1) _InVariation.Because electric current I _bCan be along with electric current I _aChange with sawtooth signal RA, so electric current I _bNeed be suitable for dutycycle D and input voltage V in the simulation equation formula (1) _InCaused threshold peak setting signal V _{Peak_TH}Variation.Electric current I _cBe a fixing compensation (Offset) electric current, be used for adjusting threshold peak setting signal V _{Peak_TH}DC level (DC Level).In one embodiment of the invention, lower boundary reference voltage V _B1Be set at 0.5 volt, coboundary reference voltage V _BhBe set at 0.75 volt and sawtooth signal RA along with the time is changed to 0.8 volt from 0 volt of linearity.Under this parameter condition, electric current I _a, I _b, and I _cCombination quite satisfactorily analog approximation in dutycycle between 0.66 to 1 threshold peak setting signal V in interval _{Peak_TH}Variation.

Please note the changeover voltage adjuster that can be widely used in various kenels in a circuit according to the invention with method, for example synchronously with asynchronous, boost and step-down, Voltage Feedback control and Current Feedback Control, pulse-length modulation (PWM) and pulse frequency modulation (PFM) or the like all conventional voltage regulator types, there is no the restriction of special kenel.Fig. 7 shows the circuit block diagram of avoiding the synchronous suitching type boost pressure controller of discontinuous mode according to of the present invention.What the boost pressure controller of Fig. 7 and the difference part of the step down voltage redulator of Fig. 4 were side switch HS and inductance L is connected form, switching logic circuit 70 and threshold peak current setting circuit 75.As shown in the figure, inductance L is connected input voltage source V _InAnd between the common node CN, side switch HS then is connected between common node CN and the output terminal.Switching logic circuit 70 provides the positive output Q of SR latch as upside drive signal HD and downside drive signal LD.75 of threshold peak current setting circuits produce threshold peak setting signal V _{Peak_TH}, be used for representing the peak I of critical conditions inductive current _{Peak_TH}, shown in following equation (9):

$I_{\mathrm{peak}\_\mathrm{TH}}=\left(\frac{T_s}{L}\right)\·D\·(1-D)\·V_{\mathrm{out}}...\left(9\right)$

Compare equation (9) and (1) as can be known, the output voltage item V of equation (9) _OutOutput voltage source item V corresponding to equation (1) _InTherefore, be applied to the threshold peak current setting circuit 75 of boost pressure controller in response to output voltage V _OutThe sawtooth signal RA that is produced with oscillatory circuit 11 and determine threshold peak setting signal V _{Peak_TH}Particularly, as long as for threshold peak current setting circuit 45-1 shown in Figure 5 or threshold peak current setting circuit 45-2 shown in Figure 6, will originally use input voltage V _InPart is changed into the use output voltage V _Out, can obtain to be applied to the threshold peak current setting circuit 75 of boost pressure controller shown in Figure 7 easily.

Though the present invention is illustrated as example by preferred embodiment, be appreciated that to the invention is not restricted to the disclosed embodiments.On the contrary, this invention is intended to contain is tangible various modification and similar configuration for a person skilled in the art.Therefore, the scope of claims should be according to the widest annotation, to comprise all this modifications and similar configuration.

Claims (9)

1, a kind of changeover voltage adjuster comprises:

A commutation circuit, operate under one first mode of operation and one second mode of operation, in described first mode of operation, described commutation circuit allows the linear increase of a switch current, and in described second mode of operation, described commutation circuit allows the linear minimizing of described switch current;

A control circuit is coupled to described commutation circuit, is used for controlling described commutation circuit and operates under described first or second mode of operation; And

An initialization circuit, be used for producing a minimum detectable signal, make described control circuit guarantee that in response to described minimum detectable signal described switch current increases to more than or equal to a current value that is set by described minimum detectable signal at the described first mode of operation neutral line, thereby prevent that described switch current is reduced to reversal of poles at the described second mode of operation neutral line, wherein said control circuit comprises:

A current feedback circuit is used for producing a current feedback signal, and it represents described switch current;

A voltage feedback circuit is used for producing a voltage feedback signal, and it represents an output voltage;

An error amplifier according to described voltage feedback signal and a reference voltage signal, is used for producing an error signal;

One first comparator circuit, more described current feedback signal and described error signal are used for producing one first compare result signal;

One second comparator circuit, more described current feedback signal and described minimum detectable signal are used for producing one second compare result signal; And

A logical circuit receives described first compare result signal and described second compare result signal, is used for triggering trigger circuit.

2, changeover voltage adjuster as claimed in claim 1, wherein:

Described changeover voltage adjuster converts an input voltage to described output voltage, and

Described initialization circuit comprises:

A linear current regulator is used for producing a current signal, and it represents described input voltage;

One first differential right, controlled by one-period signal and a lower boundary reference voltage signal, is used for choosing from described current signal one first component;

One second differential right, controlled by described periodic signal and a coboundary reference voltage signal, is used for choosing from described current signal a second component; And

A fixed current source is used to provide a compensating current signal, wherein:

Described minimum detectable signal is according to described current signal, described first component, described second component, produce with described compensating current signal.

3, changeover voltage adjuster as claimed in claim 2 further comprises:

An oscillatory circuit, be used for producing a pulse signal and a sawtooth signal, make described control circuit described commutation circuit be operated under described first mode of operation, and make described sawtooth signal as described periodic signal in response to described pulse signal.

4, changeover voltage adjuster as claimed in claim 1 further comprises:

An oscillatory circuit, be used for producing a pulse signal and a sawtooth signal, make described control circuit described commutation circuit be operated under described first mode of operation, and make described initialization circuit adjust described minimum detectable signal in response to described sawtooth signal in response to described pulse signal.

5, a kind of control method of changeover voltage adjuster comprises the following step:

Control a commutation circuit and under one first mode of operation, operate, be used for allowing the linear increase of a switch current;

Control described commutation circuit and under one second mode of operation, operate, be used for allowing the linear minimizing of described switch current;

Produce a current feedback signal, it represents described switch current;

Produce a voltage feedback signal, it represents an output voltage;

Produce a minimum detectable signal, it represents a critical current;

Produce an error signal, it represents the difference of a described voltage feedback signal and a reference voltage signal;

More described current feedback signal and described error signal are used for producing one first compare result signal; And

More described current feedback signal and described minimum detectable signal are used for producing one second compare result signal, wherein:

Described first compare result signal and described second compare result signal are used for triggering trigger circuit, and

Wherein, in the described step that the described commutation circuit of control is operated under described first mode of operation, guarantee that described switch current linearity increases to more than or equal to critical current, thereby in the described step that the described commutation circuit of control is operated, prevent that described switch current linearity is reduced to reversal of poles under described second mode of operation.

6, the control method of changeover voltage adjuster as claimed in claim 5 further comprises the following step:

When continuing the described commutation circuit of control during less than described critical current, under described first mode of operation, operates described switch current.

7, the control method of changeover voltage adjuster as claimed in claim 5, wherein:

Described critical current is adjusted based on control described commutation circuit shared time of described step of operating under described first mode of operation at least.

8, the control method of changeover voltage adjuster as claimed in claim 5, wherein:

Described changeover voltage adjuster converts an input voltage to described output voltage, makes described output voltage less than described input voltage, and

Described critical current is adjusted based on described input voltage at least.

9, the control method of changeover voltage adjuster as claimed in claim 5, wherein:

Described changeover voltage adjuster converts an input voltage to described output voltage, makes described output voltage greater than described input voltage, and

Described critical current is adjusted based on described output voltage at least.

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