CN100463342C - Reverse current prevention circuit capable of self-correcting reference benchmark - Google Patents
Reverse current prevention circuit capable of self-correcting reference benchmark Download PDFInfo
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- CN100463342C CN100463342C CNB2006100754451A CN200610075445A CN100463342C CN 100463342 C CN100463342 C CN 100463342C CN B2006100754451 A CNB2006100754451 A CN B2006100754451A CN 200610075445 A CN200610075445 A CN 200610075445A CN 100463342 C CN100463342 C CN 100463342C
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Abstract
The synchronous switch-mode voltage converter has a first switch, a second switch and an electrical inductance that are all coupled to a switch node. The circuit for preventing the reverse current includes a fixed reference current source, a correcting circuit, a circuit for generating variable reference circuit and a comparing circuit. The correcting circuit generates a correcting signal on the basis of the comparison of the electrical inductance and the fixed reference current source. The circuit generating variable reference current generates the variable reference current signals which are adjusted according to the correcting signals. A preventing signal is added to the second switch which will be in non-conduction state on the basis of the comparison of electrical inductance current and the variable reference current signals.
Description
Technical field
The present invention especially about a kind of backward current preventing circuit that is used for synchronous switched voltage converter, can revise reference data so that prevent the generation of backward current exactly about a kind of backward current preventing circuit automatically.
Background technology
Fig. 1 (a) shows the circuit diagram of known synchronous switched voltage converter 10.Synchronous switched voltage converter 10 is with input voltage source V
InConvert output voltage V to
Out, and be supplied to load Ld.Side switch SH is coupled in input voltage source V
InAnd between switching node SN, side switch SL then is coupled between switching node SN and ground potential.In the example shown in Fig. 1 (a), side switch SH is implemented side switch SL by the PMOS electric crystal and is then implemented by the NMOS crystal.Inductance L is coupled between switching node SN and output O.Control circuit 11 applies switch-over control signal CS to drive circuit 12, to produce upside drive signal PH and downside drive signal PL.The conducting and not conducting of upside drive signal PH decision side switch SH, and the conducting and not conducting of downside drive signal PL decision side switch SL.In response to output voltage V
OutFeedback, control circuit 11 is adjusted the duty cycle (Duty Cycle) of switch-over control signal CS, to regulate output voltage V
OutIn addition, output capacitance C
oBe coupled in output O, so that to output voltage V
OutCarry out filtering.
Fig. 1 (b) shows the operation waveform sequential chart of known synchronous switched voltage converter 10.Switch-over control signal CS is respectively via last side drive circuit 12H and following side drive circuit 12L and anti-phase formation upside drive signal PH and downside drive signal PL.In the stage of time T 1 to T2, upside drive signal PH and downside drive signal PL all are in low level, so side switch SH conducting and not conducting of side switch SL, make inductive current I
LDirection flow to output O (this is defined as positive direction) by switching node SN and its absolute value increases gradually.In the stage of time T 2 to T4, upside drive signal PH and downside drive signal PL all are in high level, so side switch not conducting of SH and side switch SL conducting, make inductive current I
LAbsolute value reduce gradually.Please note when time T 3 inductive current I
LAbsolute value be reduced to zero, therefore from time T 3 to T4, inductive current I
LDirection be reversed into by output O and flow to switching node SN (this is defined as negative direction).In the stage of time T 4 to T6, upside drive signal PH and downside drive signal PL all are in low level, so side switch SH conducting and not conducting of side switch SL.Owing to inductive current I this moment
LDirection for negative, so inductive current I
LAbsolute value reduce gradually.Up to from time T 5, inductive current I
LDirection just just changing into and its absolute value increases gradually.
In Fig. 1 (b), the phenomenon of the region representation generation backward current of oblique line part.As inductive current I
LDirection when flowing to switching node SN by output O, energy is by the reverse synchronous switched voltage converter 10 that is supplied to of external loading Ld.Because backward current causes the conversion efficiency of synchronous switched voltage converter 10 to reduce, so must manage to prevent the generation of backward current.
Fig. 2 (a) shows the circuit diagram of the backward current preventing circuit 23 of known first example.Backward current preventing circuit 23 has a current comparison circuit 24, a fixed reference current source I
Ref, and together or gate 25.The non-inverting input of current comparison circuit 24 is in order to the receiving inductance electric current I
L, and inverting input is in order to receive fixed reference current source I
RefWith or one of gate 25 input in order to receiving switch-over control signal CS, and the anti-stop signal RI that exported in order to received current comparison circuit 24 of another input.Output same or gate 25 is coupled to down side drive circuit 12L, with decision downside drive signal PL.
Fig. 2 (b) shows the operation waveform sequential chart of the backward current preventing circuit 23 of known first example.Suppose fixed reference current source I
RefBe set at zero.In the stage of time T 1 to T2, switch-over control signal CS is that high level and anti-stop signal RI are high level, makes upside drive signal PH and downside drive signal PL all be in low level.Therefore, side switch SH conducting and not conducting of side switch SL make inductive current I
LDirection for just and its absolute value increase gradually.At time T 2 places, switch-over control signal CS is transformed into low level, makes upside drive signal PH and downside drive signal PL all be transformed into high level.Therefore, not conducting of side switch SH and side switch SL conducting make inductive current I
LAbsolute value reduce gradually.At time T 3 places, because inductive current I
LAbsolute value be decreased to zero, so prevent that stop signal RI changes low level into and causes downside drive signal PL to become low level.Therefore, side switch SL enters not on-state to prevent inductive current I
LDirection take a turn for the worse.
Yet, because the actual operational speed of current comparison circuit 24 is limited, so inductive current I
LAbsolute value be decreased to the time point that zero time point and anti-stop signal RI are applied to side switch SL, have a time of delay between the two.In other words, in this time of delay, inductive current I
LDirection still can take a turn for the worse.The shortcoming that can't prevent backward current fully that causes time of delay is planted in the i.e. expression of oblique line part among Fig. 2 (b) thus.Moreover along with the variation of integrated circuit manufacture process itself and the variation of operating temperature, the service speed of current comparison circuit 24 also can change.As a result, be not a fixed value time of delay that current comparison circuit 24 is caused, thereby more difficultly eliminate this kind time of delay by fixing offset current (offset current) is set with expectation.
Fig. 3 (a) shows the circuit diagram of the backward current preventing circuit 33 of known second example.Backward current preventing circuit 33 has a voltage comparator circuit 34, a fixed voltage reference V
Ref, and together or gate 35.The non-inverting input of voltage comparator circuit 34 is in order to receive the voltage V at switching node SN place
SN, and inverting input is in order to receive fixed voltage reference V
RefWith or an input of gate 35 in order to receiving switch-over control signal CS, and another input is in order to receive the anti-stop signal RV that voltage comparator circuit 34 is exported.Output same or gate 35 is coupled to down side drive circuit 12L, with decision downside drive signal PL.
Fig. 3 (b) shows the operation waveform sequential chart of the backward current preventing circuit 33 of known second example.Suppose fixed voltage reference V
RefBe set at zero.In the stage of time T 1 to T2, switch-over control signal CS is that high level and anti-stop signal RV are high level, makes upside drive signal PH and downside drive signal PL all be in low level.Therefore, side switch SH conducting and not conducting of side switch SL make the voltage V at switching node SN place
SNDraw high and become to equal input voltage source V
InAt time T 2 places, switch-over control signal CS is transformed into low level, makes upside drive signal PH and downside drive signal PL all be transformed into high level.Therefore, not conducting of side switch SH and side switch SL conducting make inductive current I
LFlow to inductance L and output O from ground potential (zero potential) via side switch SL, cause the voltage V at switching node SN place
SNBecome negative polarity rapidly.Subsequently, because inductive current I
LAbsolute value reduce the voltage V at switching node SN place gradually
SNGradually towards ground potential (zero potential) convergence.At time T 3 places, because the voltage V at switching node SN place
SNReached zero potential and changed into positive polarity,, made downside drive signal PL be transformed into low level so anti-stop signal RV changes high level into.Therefore, side switch SL enters not on-state to prevent inductive current I
LDirection take a turn for the worse.
Yet, because the actual operational speed of voltage comparator circuit 34 is limited, so the voltage V at switching node SN place
SNReach the time point that zero time point and anti-stop signal RV are applied to side switch SL, have a time of delay between the two.In other words, in this time of delay, inductive current I
LDirection still can take a turn for the worse.The shortcoming that can't prevent backward current fully that causes time of delay is planted in the i.e. expression of oblique line part among Fig. 3 (b) thus.Moreover along with the variation of integrated circuit manufacture process itself and the variation of operating temperature, the service speed of voltage comparator circuit 34 also can change.As a result, be not a fixed value time of delay that voltage comparator circuit 34 is caused, thereby more difficultly eliminate this kind time of delay by fixing bucking voltage (offset voltage) is set with expectation.
Summary of the invention
In view of foregoing problems, the object of the present invention is to provide a kind of backward current preventing circuit, be applied to synchronous switched voltage converter, can revise reference data automatically so that prevent the generation of backward current exactly.
According to an aspect of of the present present invention, a kind of backward current preventing circuit is provided, be applied in the synchronous switch type electric voltage converter.This synchronous switched voltage converter has one first switch, a second switch and an inductance, and three's coupled in common is switched node in one.When this first switch conduction and this not conducting of second switch, an inductive current of this inductance of flowing through increases.When this first not conducting of switch and this second switch conducting, this inductive current then reduces.This backward current preventing circuit comprises: a fixed reference current source, a correction circuit, a circuit generating variable reference current and a comparison circuit.Based on the comparison between this inductive current and this fixed reference current source, correction circuit produces a corrected signal.Circuit generating variable reference current produces a variable reference current signals, and it is adjusted according to this corrected signal.Based on the comparison between this inductive current and this variable reference current signals, comparison circuit applies an anti-stop signal to this second switch, makes this not conducting of second switch.
According to another aspect of the present invention, a kind of backward current preventing circuit is provided, be applied in the synchronous switch type electric voltage converter.This synchronous switched voltage converter has one first switch, a second switch and an inductance, and three's coupled in common is switched node in one.When this first switch conduction and this not conducting of second switch, an inductive current of this inductance of flowing through increases.When this first not conducting of switch and this second switch conducting, this inductive current then reduces.This backward current preventing circuit comprises: a fixed voltage reference, a correction circuit, a variable reference voltage generation circuit and a comparison circuit.Based on voltage of this switching node and the comparison between this fixed voltage reference, correction circuit produces a corrected signal.The variable reference voltage generation circuit produces a variable reference voltage signal, and it is adjusted according to this corrected signal.Based on this voltage of this switching node and the comparison between this variable reference voltage signal, comparison circuit applies an anti-stop signal to this second switch, makes this not conducting of second switch.
Description of drawings
Fig. 1 (a) shows the circuit diagram of known synchronous switched voltage converter.
Fig. 1 (b) shows the operation waveform sequential chart of known synchronous switched voltage converter.
Fig. 2 (a) shows the circuit diagram of the backward current preventing circuit of known first example.
Fig. 2 (b) shows the operation waveform sequential chart of the backward current preventing circuit of known first example.
Fig. 3 (a) shows the circuit diagram of the backward current preventing circuit of known second example.
Fig. 3 (b) shows the operation waveform sequential chart of the backward current preventing circuit of known second example.
Fig. 4 shows the circuit diagram according to the backward current preventing circuit of the present invention's first example.
Fig. 5 shows the circuit diagram according to the backward current preventing circuit of the present invention's second example.
Fig. 6 shows the circuit diagram according to circuit generating variable reference current of the present invention.
Fig. 7 shows the circuit diagram according to variable reference voltage generation circuit 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 preferred embodiment of the present invention with reference to the accompanying drawings.
Fig. 4 shows the circuit diagram according to the backward current preventing circuit 43 of the present invention's first example.With reference to Fig. 4, backward current preventing circuit 43 has a current comparison circuit 44, together or gate 45, a circuit generating variable reference current 46, an electric current correction circuit 47 and a fixed reference current source I
RefThe non-inverting input of current comparison circuit 44 is in order to the receiving inductance electric current I
L, and inverting input is in order to receive the variable reference current signals I that is exported from circuit generating variable reference current 46
VarWith or an input of gate 45 in order to receiving switch-over control signal CS, and the anti-stop signal RI that exported in order to received current comparison circuit 44 of another input.Output same or gate 45 is coupled to down side drive circuit 12L, with decision downside drive signal PL.
Particularly, the variable reference current signals I that exported of circuit generating variable reference current 46
VarAdjust in response to electric current correction circuit 47.Electric current correction circuit 47 has a sample-and-hold circuit 48 and an auxiliary current comparison circuit 49.Sample-and-hold circuit 48 in response to anti-stop signal RI for inductive current I
LTake a sample.Be transformed into low level moment at anti-stop signal RI from high level, promptly make side switch SL enter not on-state to stop the moment of backward current, sample-and-hold circuit 48 is for the inductive current I of this moment
LTake a sample, as current sample signal SI.The non-inverting input of auxiliary current comparison circuit 49 is in order to received current sample signal SI, and inverting input is in order to receive fixed reference current source I
RefFor example, fixed reference current source I
RefMust be set at zero.Based on current sample signal SI and fixed reference current source I
RefBetween comparative result, auxiliary current comparison circuit 49 applies an electric current corrected signal CI to circuit generating variable reference current 46.
In response to electric current corrected signal CI, circuit generating variable reference current 46 is adjusted the variable reference current signals I that is exported
VarWhen current sample signal SI greater than fixed reference current source I
RefThe time, electric current corrected signal CI is a high level.That is, enter the moment of not on-state, inductive current I at side switch SL
LGreater than fixed reference current source I
RefIn other words, at inductive current I
LDirection do not take a turn for the worse as yet before, side switch SL too early enters not on-state.Therefore, circuit generating variable reference current 46 must make variable reference current signals I
VarReduce, the moment that makes side switch SL enter not on-state can be delayed generation.When current sample signal SI less than fixed reference current source I
RefThe time, electric current corrected signal CI is a low level.That is, enter the moment of not on-state, inductive current I at side switch SL
LLess than fixed reference current source I
RefIn other words, at inductive current I
LDirection taken a turn for the worse after, side switch SL just enters not on-state too late.Therefore, circuit generating variable reference current 46 must make variable reference current signals I
VarRaise, the moment that makes side switch SL enter not on-state can take place in advance.
Though the actual operational speed of current comparison circuit 44 is limited, and change, yet directly detect inductive current I according to electric current correction circuit 47 of the present invention along with integrated circuit technology and operating temperature
L, and based on inductive current I
LWith fixed reference current source I
RefBetween comparison and produce electric current corrected signal CI.Subsequently, in response to electric current corrected signal CI, circuit generating variable reference current 46 is able to revise automatically the variable reference current signals I that is produced
VarIn other words, revised variable reference current signals I
VarTake into account the time of delay that current comparison circuit 44 is caused, so can prevent the generation of backward current exactly according to backward current preventing circuit 43 of the present invention.
Fig. 5 shows the circuit diagram according to the backward current preventing circuit 53 of the present invention's second example.With reference to Fig. 5, backward current preventing circuit 53 has a voltage comparator circuit 54, together or gate 55, a variable reference voltage generation circuit 56, a voltage modification circuit 57 and a fixed voltage reference V
RefThe non-inverting input of voltage comparator circuit 54 is in order to receive the voltage V at switching node SN place
SN, and inverting input is in order to receive the variable reference voltage signal V that is exported from variable reference voltage generation circuit 56
VarWith or an input of gate 55 in order to receiving switch-over control signal CS, and another input is in order to receive the anti-stop signal RV that voltage comparator circuit 54 is exported.Output same or gate 55 is coupled to down side drive circuit 12L, with decision downside drive signal PL.
Particularly, the variable reference voltage signal V that exported of variable reference voltage generation circuit 56
VarAdjust in response to voltage modification circuit 57.Voltage modification circuit 57 has a sample-and-hold circuit 58 and a boost voltage comparison circuit 59.Sample-and-hold circuit 58 in response to anti-stop signal RV for the voltage V at switching node SN place
SNTake a sample.Be transformed into moment of high level at anti-stop signal RV from low level, promptly make side switch SL enter not on-state to stop the moment of backward current, sample-and-hold circuit 58 is for the voltage V at the switching node SN place of this moment
SNTake a sample, as voltage sample signal SV.The non-inverting input of boost voltage comparison circuit 59 is in order to reception voltage sample signal SV, and inverting input is in order to receive reference voltage source V
RefFor example, fixed voltage reference V
RefMust be set at zero.Based on voltage sample signal SV and fixed voltage reference V
RefBetween comparative result, boost voltage comparison circuit 59 applies a voltage corrected signal CV to variable reference voltage generation circuit 56.
In response to voltage corrected signal CV, variable reference voltage generation circuit 56 is adjusted the variable reference voltage signal V that is exported
VarWhen voltage sample signal SV greater than fixed voltage reference V
RefThe time, voltage corrected signal CV is a high level.That is, enter the moment of not on-state, the voltage V at switching node SN place at side switch SL
SNGreater than fixed voltage reference V
RefIn other words, at inductive current I
LDirection taken a turn for the worse after, side switch SL just enters not on-state too late.Therefore, variable reference voltage generation circuit 56 must make variable reference voltage signal V
VarReduce, the moment that makes side switch SL enter not on-state can take place in advance.When voltage sample signal SV less than fixed voltage reference V
RefThe time, voltage corrected signal CV is a low level.That is, enter the moment of not on-state, the voltage V at switching node SN place at side switch SL
SNLess than fixed voltage reference V
RefIn other words, at inductive current I
LDirection do not take a turn for the worse as yet before, side switch SL too early enters not on-state.Therefore, variable reference voltage generation circuit 56 must make variable reference voltage signal V
VarRaise, the moment that makes side switch SL enter not on-state can be delayed generation.
Though the actual operational speed of voltage comparator circuit 54 is limited, and change, yet directly detect the voltage V at switching node SN place according to voltage modification circuit 57 of the present invention along with integrated circuit technology and operating temperature
SN, and based on the voltage V at switching node SN place
SNWith fixed voltage reference V
RefBetween comparison and produce voltage corrected signal CV.Subsequently, in response to voltage corrected signal CV, variable reference voltage generation circuit 56 is able to revise automatically the variable reference voltage signal V that is produced
VarIn other words, revised variable reference voltage signal V
VarTake into account the time of delay that voltage comparator circuit 54 is caused, so can prevent the generation of backward current exactly according to backward current preventing circuit 53 of the present invention.
Only be illustrated though please note previous embodiment, can be applied to the synchronous switched voltage converter of pressure boosting type electric voltage converter and other kinds type according to backward current preventing circuit of the present invention for the buck electric pressure converter.
Fig. 6 shows the circuit diagram according to circuit generating variable reference current 46 of the present invention.With reference to Fig. 6, circuit generating variable reference current 46 has increase and decrease decision circuitry 60, a up-down counter 61 and a digital to analog converter 62.Increase and decrease decision circuitry 60 is in order to receive from electric current correction circuit 47 and the electric current corrected signal CI that comes, and judge based on electric current corrected signal CI should output increment signal US or decrement signals DS.
With reference to as described in Fig. 4, when the anti-stop signal RI that is produced when current comparison circuit 44 is converted to low level, the backward current incident promptly takes place as preamble, sample-and-hold circuit 48 is prevented from signal RI and starts with for inductive current I
LTake a sample.On the contrary, 60 of decision circuitry of increase and decrease are forced shut-down operation by low level anti-stop signal RI.By the time after anti-stop signal RI returned back to high level, increase and decrease decision circuitry 60 just was allowed to executable operations, should output increment signal US or decrement signals DS so that judge based on electric current corrected signal CI.Therefore, current comparison circuit 44 can use revised variable reference current signals I next time
VarDetect the generation of backward current more accurately.
Increase and decrease decision circuitry 60 is by an inverter 63 and two AND gates 64 and 65, and being coupled forms as shown in Figure 6.When electric current corrected signal CI was high level, the decrement signals DS that is produced from increase and decrease decision circuitry 60 was a high level, made the count value Num of up-down counter 61 reduce.When electric current corrected signal CI was low level, the increment signal US that is produced from increase and decrease decision circuitry 60 was a high level, made the count value Num of up-down counter 61 increase.In response to the count value Num of up-down counter 61, digital to analog converter 62 is adjusted fixed reference current source I
RefAnd the corresponding variable reference current signals I of generation
VarCount value Num is bigger, pairing variable reference current signals I
VarAlso bigger.
Fig. 7 shows the circuit diagram according to variable reference voltage generation circuit 56 of the present invention.With reference to Fig. 7, variable reference voltage generation circuit 56 has increase and decrease decision circuitry 70, a up-down counter 71 and a digital to analog converter 72.Increase and decrease decision circuitry 70 is in order to receive from voltage modification circuit 57 and the voltage corrected signal CV that comes, and judge based on voltage corrected signal CV should output increment signal US or decrement signals DS.
With reference to as described in Fig. 5, when the anti-stop signal RV that is produced when voltage comparator circuit 54 is converted to high level, the backward current incident promptly takes place as preamble, sample-and-hold circuit 58 is prevented from signal RV and starts with the voltage V for switching node SN
SNTake a sample.On the contrary, 70 anti-stop signal RV by high level of increase and decrease decision circuitry force shut-down operation.When anti-by the time stop signal RV returned back to low level, increase and decrease decision circuitry 70 is executable operations, should output increment signal US or decrement signals DS so that judge based on electric current corrected signal CI.Therefore, voltage comparator circuit 54 can use revised variable reference voltage signal V next time
VarDetect the generation of backward current more accurately.
Increase and decrease decision circuitry 70 is by two inverters 73 and 76 and two AND gates 74 and 75, and being coupled forms as shown in Figure 7.When voltage corrected signal CV was high level, the decrement signals DS that is produced from increase and decrease decision circuitry 70 was a high level, made the count value Num of up-down counter 71 reduce.When voltage corrected signal CV was low level, the increment signal US that is produced from increase and decrease decision circuitry 70 was a high level, made the count value Num of up-down counter 71 increase.In response to the count value Num of up-down counter 71, digital to analog converter 72 is adjusted fixed voltage reference V
RefAnd the corresponding variable reference voltage signal V of generation
VarCount value Num is bigger, pairing variable reference voltage signal V
VarAlso bigger.
Though the present invention was illustrated as illustration by preferred embodiment already, should be appreciated that to the invention is not restricted to the embodiment that this is disclosed.On the contrary, this invention is intended to contain tangible to those skilled in the art various modifications and similar configuration.Therefore, the scope of claim should be according to the widest annotation, and this type of is revised and similar configuration to contain all.
Claims (6)
1. backward current preventing circuit, be applied in the synchronous switch type electric voltage converter, this synchronous switched voltage converter has one first switch, a second switch and an inductance, three's coupled in common is switched node in one, make that when this first switch conduction and this not conducting of second switch, an inductive current of this inductance of flowing through increases, and when this first not conducting of switch and this second switch conducting, this inductive current then reduces, and this backward current preventing circuit comprises:
One fixed reference current source;
One electric current correction circuit in order to when this second switch enters not on-state in response to an anti-stop signal, produces an electric current corrected signal based on the comparison between the electric current of this inductive current and this fixed reference current source;
One circuit generating variable reference current, in order to produce a variable reference current signals, it is adjusted according to this electric current corrected signal, when this electric current correction circuit detects this inductive current greater than the electric current of this fixed reference current source, this circuit generating variable reference current reduces this variable reference current signals in response to this electric current corrected signal, and when this electric current correction circuit detected this inductive current less than the electric current of this fixed reference current source, this circuit generating variable reference current improved this variable reference current signals in response to this electric current corrected signal; And
One comparison circuit in order to produce this anti-stop signal based on the comparison between this inductive current and this variable reference current signals, makes this not conducting of second switch.
2. backward current preventing circuit as claimed in claim 1, wherein:
This electric current correction circuit comprises:
One sample-and-hold circuit in order to when this second switch enters not on-state in response to this anti-stop signal, produces a current sample signal, its representative this inductive current when this comparison circuit applies this anti-stop signal, and
One auxiliary comparison circuit is in order to produce this electric current corrected signal based on the comparison between the electric current of this current sample signal and this fixed reference current source.
3. backward current preventing circuit as claimed in claim 1, wherein:
This circuit generating variable reference current comprises:
One increase and decrease decision circuitry, in order to produce an increment signal and a decrement signals in response to this electric current corrected signal, wherein when this electric current corrected signal is in one first level, this increase and decrease decision circuitry produces this increment signal, and when this electric current corrected signal was in one second level, this increase and decrease decision circuitry produced this decrement signals;
One up-down counter, in order to produce a count value, wherein when this up-down counter received this increment signal, this count value increased, and when this up-down counter received this decrement signals, this count value reduced; And
One digital to analog converter is in order to produce this variable reference current signals according to this count value.
4. backward current preventing circuit, be applied in the synchronous switch type electric voltage converter, this synchronous switched voltage converter has one first switch, a second switch and an inductance, three's coupled in common is switched node in one, make that when this first switch conduction and this not conducting of second switch, an inductive current of this inductance of flowing through increases, and when this first not conducting of switch and this second switch conducting, this inductive current then reduces, and this backward current preventing circuit comprises:
One fixed voltage reference;
One voltage modification circuit in order to when this second switch enters not on-state in response to an anti-stop signal, produces a voltage corrected signal based on the comparison between the voltage of a voltage of this switching node and this fixed voltage reference;
One variable reference voltage generation circuit, in order to produce a variable reference voltage signal, it is adjusted according to this voltage corrected signal, this voltage that detects this switching node when this voltage modification circuit is during greater than the voltage of this fixed voltage reference, this variable reference voltage generation circuit reduces this variable reference voltage signal in response to this voltage corrected signal, and this voltage that detects this switching node when this voltage modification circuit is during less than the voltage of this fixed voltage reference, and this variable reference voltage generation circuit improves this variable reference voltage signal in response to this voltage corrected signal; And
One comparison circuit in order to based on this voltage of this switching node and the comparison between this variable reference voltage signal and produce this anti-stop signal, makes this not conducting of second switch.
5. backward current preventing circuit as claimed in claim 4, wherein:
This voltage modification circuit comprises:
One sample-and-hold circuit in order to when this second switch enters not on-state in response to this anti-stop signal, produces a voltage sample signal, this voltage of its representative this switching node when this comparison circuit applies this anti-stop signal, and
One auxiliary comparison circuit is in order to produce this voltage corrected signal based on the comparison between the voltage of this voltage sample signal and this fixed voltage reference.
6. backward current preventing circuit as claimed in claim 4, wherein:
This variable reference voltage generation circuit comprises:
One increase and decrease decision circuitry, in order to produce an increment signal and a decrement signals in response to this voltage corrected signal, wherein when this voltage corrected signal is in one first level, this increase and decrease decision circuitry produces this increment signal, and when this voltage corrected signal was in one second level, this increase and decrease decision circuitry produced this decrement signals;
One up-down counter, in order to produce a count value, wherein when this up-down counter received this increment signal, this count value increased, and when this up-down counter received this decrement signals, this count value reduced; And
One digital to analog converter is in order to produce this variable reference voltage signal according to this count value.
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| Application Number | Priority Date | Filing Date | Title |
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| CNB2006100754451A CN100463342C (en) | 2006-04-14 | 2006-04-14 | Reverse current prevention circuit capable of self-correcting reference benchmark |
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|---|---|---|---|
| CNB2006100754451A CN100463342C (en) | 2006-04-14 | 2006-04-14 | Reverse current prevention circuit capable of self-correcting reference benchmark |
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| CN100463342C true CN100463342C (en) | 2009-02-18 |
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| US8278897B2 (en) * | 2009-12-17 | 2012-10-02 | Semiconductor Components Industries, Llc | Power supply converter and method |
| US20130063116A1 (en) * | 2011-09-14 | 2013-03-14 | Fairchild Semiconductor Corporation | True reverse current blocking system |
| CN107124112B (en) * | 2016-02-24 | 2020-02-07 | 炬芯（珠海）科技有限公司 | Control method and control circuit of comparator |
| CN109217668B (en) * | 2017-06-29 | 2020-06-30 | 立锜科技股份有限公司 | Switching type power supply capable of adjusting inductive current threshold and control method |
| CN108599570B (en) * | 2018-06-04 | 2019-10-22 | 电子科技大学 | A kind of circuit with dynamic regulation current limit threshold |
| CN109936293B (en) * | 2019-02-28 | 2020-06-16 | 西安微电子技术研究所 | Level conversion circuit and voltage transformation output DC/DC converter power module based on same |
| TWI707529B (en) * | 2020-05-05 | 2020-10-11 | 立錡科技股份有限公司 | Switching power conversion circuit and switching circuit |
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| US20060071651A1 (en) * | 2004-09-30 | 2006-04-06 | Fujitsu Limited | Control circuit of dc-dc converter and control method thereof |
-
2006
- 2006-04-14 CN CNB2006100754451A patent/CN100463342C/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5481178A (en) * | 1993-03-23 | 1996-01-02 | Linear Technology Corporation | Control circuit and method for maintaining high efficiency over broad current ranges in a switching regulator circuit |
| US6541947B1 (en) * | 1998-09-10 | 2003-04-01 | Robert Bosch Gmbh | Step-down constant-current transformer |
| US20040000895A1 (en) * | 2002-06-28 | 2004-01-01 | Thovane Solivan | Method and apparatus for operating a voltage regulator based on inductor current detection |
| US20060071651A1 (en) * | 2004-09-30 | 2006-04-06 | Fujitsu Limited | Control circuit of dc-dc converter and control method thereof |
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|---|---|
| CN101056055A (en) | 2007-10-17 |
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