CN103701312A - Current limiting circuit and method of boost converter - Google Patents
Current limiting circuit and method of boost converter Download PDFInfo
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- CN103701312A CN103701312A CN201310743640.7A CN201310743640A CN103701312A CN 103701312 A CN103701312 A CN 103701312A CN 201310743640 A CN201310743640 A CN 201310743640A CN 103701312 A CN103701312 A CN 103701312A
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Abstract
The invention provides a current limiting circuit and method of a boost converter. The boost converter comprises a switching tube, a freewheeling tube and a master control circuit; the current limiting circuit of the boost converter comprises a first test comparison unit, a second test comparison unit and the master control circuit, wherein the first test comparison unit is suitable for producing a first current limiting signal when the current flowing through the switching tube is larger than or equal to a first cut-off current; the second test comparison unit is suitable for producing a second current limiting signal when the current flowing through the freewheeling tube is larger or equal to a second cut-off current and producing a third current limiting signal when the current flowing through the freewheeling tube is decreased to a threshold current; the master control circuit is suitable for producing a gate drive signal of the switching tube and a gate drive signal of the freewheeling tube according to a clock signal, the first current limiting signal, the second current limiting signal and the third current limiting signal. The current limiting circuit and method of the boost converter, provided by the invention, conduct current limit control on both the switching tube and the freewheeling tube in the boost converter, so as to realize current limitation within a full load scope.
Description
Technical field
The present invention relates to booster converter, particularly a kind of current-limiting circuit of booster converter and method.
Background technology
Booster converter (the boost converter) is widely used in portable set, and Fig. 1 is the electrical block diagram of common a kind of booster converter.With reference to figure 1, described booster converter comprises energy storage inductor L, switching tube Q1, continued flow tube Q2, output capacitance Cout and governor circuit 10, wherein, described governor circuit 10 is suitable for to described switching tube Q1 and continued flow tube Q2, providing gate drive signal under the control of clock signal clk, controls conducting and the cut-off of described switching tube Q1 and continued flow tube Q2.
Fig. 2 is inductive current (flowing through the electric current of the described energy storage inductor L) I of the booster converter shown in Fig. 1
lt changes in time is related to schematic diagram.With reference to figure 2, the work period Ts of described booster converter is divided into energy storage stage and afterflow stage: in the energy storage stage, described governor circuit 10 is controlled described switching tube Q1 conducting, continued flow tube Q2 cut-off, due to the effect of input voltage vin, and described inductive current I
lbeing linear increases, and electric energy conversion is that magnetic field energy is stored in described energy storage inductor L; In the afterflow stage, described governor circuit 10 is controlled described switching tube Q1 cut-off, continued flow tube Q2 conducting, due to described inductive current I
lcan not undergo mutation, described inductive current I
lthrough described continued flow tube Q2, give described output capacitance Cout and load supplying, be linear and decline.Until the next work period, described inductive current I
lagain being linear increases, and repeats said process.By regulating the ON time of described switching tube Q1 and described continued flow tube Q2, can produce stable output voltage V out.
In the work period of described booster converter Ts, the ON time Ton=D1*Ts of described switching tube Q1, Toff=D2*Ts deadline of described switching tube Q1, wherein, D1 is ON time duty ratio, and D2 is duty ratio deadline, under continuous operation mode, D1+D2=1.When described switching tube Q1 is in conducting state, the voltage at described energy storage inductor L two ends equals described input voltage vin, described inductive current I
lincrement be:
I
l+=Uin*Ton/l=Uin*D1*Ts/l------(formula 1),
Wherein, I
l+for described inductive current I
lincrement, the magnitude of voltage that Uin is described input voltage vin, l is the inductance value of described energy storage inductor L; When described switching tube Q1 is in cut-off state, the voltage at described energy storage inductor L two ends equals the voltage difference of described output voltage V out and described input voltage vin, described inductive current I
ldecrement be:
I
l-=(Uout-Uin) * Toff/l=(Uout-Uin) * D2*Ts/l------(formula 2),
Wherein, I
l-for described inductive current I
ldecrement, the magnitude of voltage that Uout is described output voltage V out.During stable state, according to the weber balance principle of inductance, described inductive current I
lincrement I
l+with described inductive current I
ldecrement I
l-equate, by formula 1 and formula 2, obtained:
Uout/Uin=1/(1-D1)------(formula 3).
Described switching tube Q1 and described continued flow tube Q2 be generally the high power devices such as MOSFET or IGBT, when making to manage self-energy if these power devices electric current has at work exceeded the ability to bear of itself and building up, as easy as rolling off a logly causes snowslide and damage device.Therefore, current limliting is the key that affects power device reliability service, can prevent from damaging because overload or output short-circuit cause described booster converter.
Fig. 3 is the electrical block diagram of the current-limiting circuit of the booster converter shown in Fig. 1.With reference to figure 3, described current-limiting circuit comprises detection comparing unit 30.Described detection comparing unit 30 is suitable for detecting the electric current that flows through described switching tube Q1, and will flowing through the electric current of described switching tube Q1 and the cut-off current Imax of setting compares to obtain current limliting signal Reset, described current limliting signal Reset controls described switching tube Q1 and continued flow tube Q2 by described governor circuit 10.Described governor circuit 10 can adopt rest-set flip-flop to realize, the set end S of described rest-set flip-flop is suitable for receiving described current limliting signal Reset, the reset terminal R of described rest-set flip-flop is suitable for receiving described clock signal clk, the first output Q of described rest-set flip-flop is suitable for providing gate drive signal to described switching tube Q1, and the second output Qn of described rest-set flip-flop is suitable for providing gate drive signal to described continued flow tube Q2.
Particularly, when flowing through the electric current of described switching tube Q1 and be more than or equal to described cut-off current Imax, described detection comparing unit 30 produces described current limliting signal Reset, by described governor circuit 10, control described switching tube Q1 cut-off, continued flow tube Q2 conducting, the energy that the ON time Ton of described switching tube Q1 is reduced, store reduces, so that the energy that the ON time of described continued flow tube Q2 (being Toff deadline of described switching tube Q1) increases, discharges increases, the energy of final storage and the energy balance of release, reach the object of Limited Current; When flowing through the electric current of described switching tube Q1 and be less than described cut-off current Imax, described detection comparing unit 30 can not produce described current limliting signal Reset, the conducting of described switching tube Q1 and continued flow tube Q2 or cut-off self determine by described governor circuit 10, and described switching tube Q1 and continued flow tube Q2 are in set time conducting or cut-off.
Yet the current-limiting circuit shown in Fig. 3 can not realize current-limiting function in full-load range, when the load of described booster converter increases the weight of, described current-limiting circuit cannot realize current limliting.
Summary of the invention
The present invention solves is the problem that the current-limiting circuit of existing booster converter cannot current limliting in full-load range.
For addressing the above problem, the invention provides a kind of current-limiting circuit of booster converter, described booster converter comprises switching tube, continued flow tube and governor circuit, the current-limiting circuit of described booster converter comprises:
First detects comparing unit, is suitable for detecting the electric current that flows through described switching tube, produces the first current limliting signal when the electric current that flows through described switching tube is more than or equal to the first cut-off current;
Second detects comparing unit, be suitable for detecting the electric current that flows through described continued flow tube, when being more than or equal to the second cut-off current, the electric current that flows through described continued flow tube produces the second current limliting signal, when the electric current that flows through described continued flow tube drops to threshold current, produce the 3rd current limliting signal, described the second cut-off current is greater than described the first cut-off current;
Described governor circuit is suitable for producing the gate drive signal of described switching tube and the gate drive signal of described continued flow tube according to clock signal, described the first current limliting signal, described the second current limliting signal and described the 3rd current limliting signal, when receiving described the first current limliting signal, control described switching tube cut-off, continued flow tube conducting, when described clock signal period finishes and receive described the second current limliting signal, keep described switching tube cut-off, continued flow tube conducting, when receiving described the 3rd current limliting signal, control described switching tube conducting, continued flow tube cut-off.
Optionally, described threshold current is less than or equal to described the second cut-off current.
Optionally, described governor circuit is rest-set flip-flop;
The reset terminal of described rest-set flip-flop is suitable for inputting described clock signal, the first set end of described rest-set flip-flop is suitable for inputting described the first current limliting signal, the second set end of described rest-set flip-flop is suitable for inputting described the second current limliting signal or described the 3rd current limliting signal, the first output of described rest-set flip-flop is suitable for exporting the gate drive signal of described switching tube, and the second output of described rest-set flip-flop is suitable for exporting the gate drive signal of described continued flow tube.
Optionally, described governor circuit is also suitable for controlling described switching tube conducting, continued flow tube cut-off when described clock signal period finishes and do not receive described the second current limliting signal.
Optionally, described switching tube and continued flow tube are metal-oxide-semiconductor.
Optionally, described switching tube and continued flow tube are IGBT.
The present invention also provides a kind of current-limiting method of booster converter, and described booster converter comprises switching tube and continued flow tube, and the current-limiting method of described booster converter comprises:
At described switching tube conducting, continued flow tube, between the off period, detect the electric current that flows through described switching tube, when the electric current that flows through described switching tube is more than or equal to the first cut-off current, control described switching tube cut-off, continued flow tube conducting;
When described booster converter work at present end cycle, the electric current of described continued flow tube is flow through in judgement:
If flow through the electric current of described continued flow tube, be less than the second cut-off current, control described switching tube conducting, continued flow tube cut-off, enter the next work period, described the second cut-off current is greater than described the first cut-off current;
If flow through the electric current of described continued flow tube, be more than or equal to described the second cut-off current, keep described switching tube conducting, continued flow tube cut-off, until when flowing through the electric current of described continued flow tube and dropping to threshold current, control described switching tube conducting, continued flow tube cut-off, enter the next work period.
Optionally, described threshold current is less than or equal to described the second cut-off current.
Compared with prior art, technical scheme of the present invention has the following advantages:
In prior art, only the switching tube in booster converter is carried out current-limiting circuit and the method for Current limited Control, the current-limiting circuit that technical solution of the present invention provides and method all will be carried out Current limited Control to the switching tube in booster converter and continued flow tube.When the load of described booster converter increases, first the inductive current of described booster converter reaches the first cut-off current, controls described switching tube cut-off, carries out the current limliting of Cycle by Cycle.Along with the continuous increase of load, inductive current still can increase.When inductive current is increased to the second cut-off current, control described continued flow tube current limliting.During described continued flow tube current limliting, described continued flow tube is in conducting state, until described inductive current drops to threshold current, then controls described switching tube conducting.Because described continued flow tube current limliting is no longer Cycle by Cycle current limliting, but relevant with the size of described inductive current, therefore, the current-limiting circuit that technical solution of the present invention provides and method can current limlitings in full-load range.
Accompanying drawing explanation
Fig. 1 is the electrical block diagram of common a kind of booster converter;
Fig. 2 is the time dependent schematic diagram that is related to of the inductive current of the booster converter shown in Fig. 1;
Fig. 3 is the electrical block diagram of the current-limiting circuit of the booster converter shown in Fig. 1;
Output voltage, clock signal, the gate drive signal of switching tube and the waveform schematic diagram of inductive current of booster converter described in when Fig. 4 is the current-limiting circuit current limliting adopting shown in Fig. 3;
Fig. 5 adopts the current-limiting circuit shown in Fig. 3 booster converter to be carried out to the method schematic diagram of current limliting;
Fig. 6 is the electrical block diagram of current-limiting circuit of the booster converter of embodiment of the present invention;
Fig. 7 be while adopting the current-limiting circuit current limliting of embodiment of the present invention described in output voltage, clock signal, the gate drive signal of switching tube and the waveform schematic diagram of inductive current of booster converter;
Fig. 8 is a kind of electrical block diagram that first of the embodiment of the present invention detects comparing unit;
Fig. 9 is the schematic flow sheet of current-limiting method of the booster converter of embodiment of the present invention.
Embodiment
Just as described in the background art, the current-limiting circuit shown in Fig. 3 can not realize current-limiting function in full-load range.Gate drive signal Drvn and the inductive current I of the output voltage V out of booster converter, clock signal clk, switching tube Q1 when Fig. 4 is the current-limiting circuit current limliting adopting shown in Fig. 3
lwaveform schematic diagram.With reference to figure 4, within each work period of described booster converter, described switching tube Q1 is constant time conducting; When detecting the electric current that flows through described switching tube Q1, described detection comparing unit 30 is more than or equal to described cut-off current Imax, described governor circuit 10 is under the control of described current limliting signal Reset, control described switching tube Q1 cut-off, continued flow tube Q2 conducting, make described booster converter electric discharge, reach the object of current limliting.
Along with the load of described booster converter constantly increases, restriction due to metering function and described booster converter self driving force of described detection comparing unit 30, described output voltage V out reduces gradually, according to formula 3, and corresponding the reducing of described ON time duty ratio D1.Therefore, the time of described switching tube Q1 cut-off is morning more and more, and the ON time Ton of described switching tube Q1 is shorter and shorter.
In described boost converter, once described switching tube Q1 conducting, at least need to wait for that minimum ON time Tom could end, described minimum ON time Tom is mainly that the logical time delay of setting up time delay and described governor circuit 10 by described detection comparing unit 30 causes.Before the ON time Ton of described switching tube Q1 reaches described minimum ON time Tom, described booster converter still can meet the weber balance principle of inductance, meets described inductive current I
lincrement I
l+with described inductive current I
ldecrement I
l-equal condition.Until the ON time Ton of described switching tube Q1 is decreased to described minimum ON time Tom, equate, the ON time Ton of described switching tube Q1 cannot reduce again, just there will be situation as shown in Figure 4:
I
l+=Uin*Tom/l------(formula 4),
I
l-=(Uout-Uin) * (Ts-Tom)/l------(formula 5).
From formula 4, described inductive current I
lincrement I
l+keep invariable; From formula 5, described inductive current I
ldecrement I
l-will reduce along with the decline of described output voltage V out.That is to say, along with the decline of described output voltage V out, within each work period of described booster converter, described inductive current I
ldecrement I
l-be less than described inductive current I
lincrement I
l+, i.e. I
l+> I
l-although, described inductive current I
lreached described cut-off current Imax, described inductive current I
lalong with described output voltage V out reduce still can increase.
Fig. 5 adopts the current-limiting circuit shown in Fig. 3 the booster converter shown in Fig. 1 to be carried out to the method schematic diagram of current limliting.With reference to figure 5, adopt the current-limiting circuit shown in Fig. 3 to carry out current limliting to described booster converter, in described switching tube Q1 conducting, between the continued flow tube Q2 off period, the electric current of described switching tube Q1 is flow through in detection, when the electric current that flows through described switching tube Q1 is more than or equal to cut-off current Imax, control described switching tube Q1 cut-off, continued flow tube Q2 conducting; During current limliting, described switching tube Q1 is in the constant time conducting of each work period, and when the rising edge of described clock signal clk arrives, described switching tube Q1 conducting, continued flow tube Q2 cut-off, enter the next work period.As can be seen from Figure 5, the current-limiting circuit shown in Fig. 3 is that Cycle by Cycle carries out current limliting, only described switching tube Q1 has been carried out to Current limited Control.
Technical solution of the present invention provides a kind of current-limiting circuit of booster converter, by the switching tube in described booster converter and continued flow tube, all carry out Current limited Control, make the inductive current of Current limited Control and described booster converter relevant, realize the current limliting in full-load range.
For above-mentioned purpose of the present invention, feature and advantage can more be become apparent, below in conjunction with accompanying drawing, specific embodiments of the invention are described in detail.
Fig. 6 is the electrical block diagram of current-limiting circuit of the booster converter of embodiment of the present invention.With reference to figure 6, described booster converter comprises energy storage inductor L, switching tube Q1, continued flow tube Q2, output capacitance Cout and governor circuit 60.Described switching tube Q1 and continued flow tube Q2 can be metal-oxide-semiconductors, can be also IGBT, can also be other high power devices with switching function, and the present invention is not construed as limiting this.The operation principle of described booster converter can, with reference to the description to Fig. 1, not repeat them here.
In the work period of described booster converter Ts, the ON time Ton of described switching tube Q1 is also the deadline of described continued flow tube Q2, and Toff deadline of described switching tube Q1 is also the ON time of described continued flow tube Q2.Therefore, the gate drive signal of described switching tube Q1 can be identical with the gate drive signal of described continued flow tube Q2, also inversion signal each other.
Particularly, when described switching tube Q1 and the continued flow tube Q2 power device that is identical polar, take metal-oxide-semiconductor as example, and described switching tube Q1 and continued flow tube Q2 are NMOS pipe or are PMOS pipe, the gate drive signal of the gate drive signal of described switching tube Q1 and described continued flow tube Q2 inversion signal each other; When described switching tube Q1 and the continued flow tube Q2 power device that is opposite polarity, or take metal-oxide-semiconductor as example, described switching tube Q1 is that NMOS pipe, continued flow tube Q2 are that PMOS pipe or described switching tube Q1 are that PMOS pipe, continued flow tube Q2 are NMOS pipe, and the gate drive signal of described switching tube Q1 is identical with the gate drive signal of described continued flow tube Q2.In embodiments of the present invention, described switching tube Q1 and continued flow tube Q2 are NMOS pipe.
The current-limiting circuit of described booster converter comprises that the first detection comparing unit 61 and second detects comparing unit 62.Particularly, described first detects comparing unit 61 is suitable for detecting the electric current that flows through described switching tube Q1, produces the first current limliting signal Reset1 when the electric current that flows through described switching tube Q1 is more than or equal to the first cut-off current Imax1; Described second detects comparing unit 62 is suitable for detecting the electric current that flows through described continued flow tube Q2, when being more than or equal to the second cut-off current Imax2, the electric current that flows through described continued flow tube Q2 produces the second current limliting signal Reset2, when the electric current that flows through described continued flow tube Q2 drops to threshold current, produce the 3rd current limliting signal Reset3, described the second cut-off current Imax2 is greater than described the first cut-off current Imax1.
Described governor circuit 60 is suitable for receive clock signal CLK, described the first current limliting signal Reset1, described the second current limliting signal Reset2 and described the 3rd current limliting signal Reset3.When described booster converter does not need current limliting, i.e. the inductive current of described booster converter (flowing through the electric current of described energy storage inductor L) I
ldo not surpass the current value of setting, described governor circuit 60 produces the gate drive signal of described switching tube Q1 and the gate drive signal of described continued flow tube Q2 according to described clock signal clk, controls the constant time conducting of described switching tube Q1 in each work period; When described booster converter is carried out to current limliting, described governor circuit 60 produces the gate drive signal of described switching tube Q1 and the gate drive signal of described continued flow tube Q2 according to described the first current limliting signal Reset1, described the second current limliting signal Reset2 and described the 3rd current limliting signal Reset3.
Particularly, in described switching tube Q1 conducting, between the continued flow tube Q2 off period, if described governor circuit 60 does not receive described the first current limliting signal Reset1, represent that the electric current flow through described switching tube Q1 is less than described the first cut-off current Imax1, described governor circuit 60 control described switching tube Q1 at set time cut-off, continued flow tube Q2 in set time conducting; If described governor circuit 60 receives described the first current limliting signal Reset1, represent that the electric current that flows through described switching tube Q1 is more than or equal to described the first cut-off current Imax1, described governor circuit 60 is controlled described switching tube Q1 cut-off, continued flow tube Q2 conducting.
When the described clock signal clk cycle (being the work period of described booster converter) finishes, if described governor circuit 60 does not receive described the second current limliting signal Reset2, represent that the electric current that flows through described continued flow tube Q2 is less than described the second cut-off current Imax2, described governor circuit 60 is controlled described switching tube Q1 conducting, continued flow tube Q2 cut-off, enters the next work period; If described governor circuit 60 receives described the second current limliting signal Reset2, represent that the electric current that flows through described continued flow tube Q2 is more than or equal to described the second cut-off current Imax2, switching tube Q1 cut-off, continued flow tube Q2 conducting described in described governor circuit 60 retentive controls, described booster converter continues electric discharge.
At described booster converter, continue in discharge process, if described governor circuit 60 does not receive described the 3rd current limliting signal Reset3, represent that the electric current flow through described continued flow tube Q2 is still greater than described threshold current, switching tube Q1 cut-off described in described governor circuit 60 retentive controls, continued flow tube Q2 conducting; If described governor circuit 60 receives described the 3rd current limliting signal Reset3, the electric current that represents to flow through described continued flow tube Q2 drops to described threshold current and equates, described governor circuit 60 is controlled described switching tube Q1 conducting, continued flow tube Q2 cut-off, enters the next work period.Described threshold current can be set according to the actual requirements, is less than or equal to described the second cut-off current Imax2.
The current-limiting circuit of the booster converter that technical solution of the present invention provides, in described switching tube Q1 conduction period, described first detects comparing unit 61 works, when flowing through the electric current of described switching tube Q1, be more than or equal to described the first cut-off current Imax1, described governor circuit 60 is controlled described switching tube Q1 shutoff, continued flow tube Q2 cut-off, make described booster converter electric discharge, reach the object of current limliting.
But different with current-limiting mode of the prior art, the current-limiting circuit of the booster converter that technical solution of the present invention provides not is after a work period finishes, to control described continued flow tube Q2 automatic cut-off, switching tube Q1 conducting again, but in described continued flow tube Q2 conduction period, detect and flow through the electric current of described continued flow tube Q2 and judge.After a work period finishes, if flow through the electric current of described continued flow tube Q2, be less than described the second cut-off current Imax2, similar with current-limiting mode of the prior art---after work at present end cycle, control described continued flow tube Q2 cut-off, switching tube Q1 conducting again; If flow through the electric current of described continued flow tube Q2, be more than or equal to described the second cut-off current Imax2, keep described continued flow tube Q2 conducting always, until flow through the electric current of described continued flow tube Q2, drop to and just control described continued flow tube Q2 cut-off, switching tube Q1 conducting again after described threshold current.
It should be noted that, described the first current limliting signal Reset1, the second current limliting signal Reset2 and the 3rd current limliting signal Reset3 can be analog voltage signal, can be also digital voltage signal.When described the first current limliting signal Reset1, the second current limliting signal Reset2 and the 3rd current limliting signal Reset3 are digital voltage signal, described governor circuit 60 can be logic control circuit.In embodiments of the present invention, described governor circuit 60 is rest-set flip-flop.The reset terminal R of described rest-set flip-flop is suitable for inputting described clock signal clk, the first set end S1 of described rest-set flip-flop is suitable for inputting described the first current limliting signal Reset1, the second set end S2 of described rest-set flip-flop is suitable for inputting described the second current limliting signal Reset2 or described the 3rd current limliting signal Reset3, the first output Q of described rest-set flip-flop is suitable for exporting the gate drive signal of described switching tube Q1, and the second output Qn of described rest-set flip-flop is suitable for exporting the gate drive signal of described continued flow tube Q2.The logic circuit structure of described rest-set flip-flop inside, for those skilled in the art know, does not repeat them here.
Fig. 7 be while adopting the current-limiting circuit current limliting of embodiment of the present invention described in output voltage V out, the clock signal clk of booster converter, gate drive signal Drvn and the inductive current I of switching tube Q1
lwaveform schematic diagram.With reference to figure 7, in described switching tube Q1 conducting, between the continued flow tube Q2 off period, described inductive current I
lbe the electric current that flows through described switching tube Q1; In described switching tube Q1 cut-off, continued flow tube Q2 conduction period, described inductive current I
lbe the electric current that flows through described continued flow tube Q2.
Within each work period of described booster converter, described switching tube Q1 is constant time conducting.Along with the load of described booster converter constantly increases, described inductive current I
lfirst be increased to and be more than or equal to described the first cut-off current Imax1, the current limliting of described switching tube Q1 starts to work, and current limliting is now Cycle by Cycle.
Load continuation increase along with described booster converter, due to described the first detection metering function of comparing unit 61 and restriction of described booster converter self driving force, described output voltage V out reduces gradually, according to formula 3, and corresponding the reducing of described ON time duty ratio D1.Therefore, the time of described switching tube Q1 cut-off is morning more and more, and the ON time Ton of described switching tube Q1 is shorter and shorter.Until the ON time Ton of described switching tube Q1 is decreased to minimum ON time Tom, equate, the ON time Ton of described switching tube Q1 cannot reduce again, described inductive current I
lstill can increase.
As described inductive current I
lbe increased to and be more than or equal to described the second cut-off current Imax2, the current limliting of described continued flow tube Q2 starts to work.During described continued flow tube Q2 current limliting, described continued flow tube Q2 is always in conducting state, until after a work period finishes described inductive current I
ldrop to described threshold current, just control described continued flow tube Q2 cut-off, switching tube Q1 conducting.The current-limiting circuit of the booster converter that technical solution of the present invention provides is no longer Cycle by Cycle current limliting, but and described inductive current I
lsize relevant, realized the current limliting in full-load range.
Fig. 8 is the described first a kind of electrical block diagram that detects comparing unit 61 that the embodiment of the present invention provides.With reference to figure 8, described first detects comparing unit 61 comprises a NMOS pipe N11, the 2nd NMOS pipe N12, the 3rd NMOS pipe N13, the 4th NMOS pipe N14, a PMOS pipe P11, the 2nd PMOS pipe P12, the first resistance R 11, the second resistance R 12, the 3rd resistance R 13, the 4th resistance R 14, the first current source I1, the second current source I2 and voltage comparator comp.Supply voltage VDD is suitable for detecting comparing unit 61 to described first and powers, and reference voltage Vref is the voltage as benchmark that corresponding described the first cut-off current Imax1 arranges.The described first concrete annexation that detects each device in comparing unit 61 can be with reference to shown in figure 8, and its operation principle, for those skilled in the art know, does not repeat them here.The described second particular circuit configurations that detects comparing unit 62 can be similar with the structure of described the first detection comparing unit 61, at this, do not do too much explanation.
It should be noted that, the described first particular circuit configurations that detects comparing unit 61 and described the second detection comparing unit 62 is not limited to the cited circuit structure of the embodiment of the present invention, in other embodiments, can also adopt other circuit structures, as long as can realize current detecting and voltage ratio function, the present invention is not construed as limiting this.
The present invention also provides a kind of current-limiting method of booster converter, and described booster converter comprises switching tube and continued flow tube, and the schematic flow sheet of the current-limiting method of described booster converter as shown in Figure 9.With reference to figure 9, the current-limiting method of described booster converter comprises:
At described switching tube conducting, continued flow tube, between the off period, detect the electric current that flows through described switching tube, when the electric current that flows through described switching tube is more than or equal to the first cut-off current, control described switching tube cut-off, continued flow tube conducting;
When described booster converter work at present end cycle, the electric current of described continued flow tube is flow through in judgement:
If flow through the electric current of described continued flow tube, be less than the second cut-off current, control described switching tube conducting, continued flow tube cut-off, enter the next work period, described the second cut-off current is greater than described the first cut-off current;
If flow through the electric current of described continued flow tube, be more than or equal to described the second cut-off current, keep described switching tube conducting, continued flow tube cut-off, until when flowing through the electric current of described continued flow tube and dropping to threshold current, control described switching tube conducting, continued flow tube cut-off, enter the next work period.Described threshold current is less than or equal to described the second cut-off current.
The operation principle of the current limliting principle of the current-limiting method of described booster converter and the current-limiting circuit of aforementioned booster converter is similar, can, with reference to the description to Fig. 6 and Fig. 7, not repeat them here.
In sum, the current-limiting circuit of the booster converter that technical solution of the present invention provides and method, to the switching tube in booster converter and continued flow tube, all to carry out Current limited Control, Current limited Control is relevant to the size of described inductive current, therefore the current-limiting circuit that, technical solution of the present invention provides and method can current limlitings in full-load range.
Although the present invention discloses as above, the present invention is not defined in this.Any those skilled in the art, without departing from the spirit and scope of the present invention, all can make various changes or modifications, so protection scope of the present invention should be as the criterion with claim limited range.
Claims (8)
1. a current-limiting circuit for booster converter, described booster converter comprises switching tube, continued flow tube and governor circuit, it is characterized in that, the current-limiting circuit of described booster converter comprises:
First detects comparing unit, is suitable for detecting the electric current that flows through described switching tube, produces the first current limliting signal when the electric current that flows through described switching tube is more than or equal to the first cut-off current;
Second detects comparing unit, be suitable for detecting the electric current that flows through described continued flow tube, when being more than or equal to the second cut-off current, the electric current that flows through described continued flow tube produces the second current limliting signal, when the electric current that flows through described continued flow tube drops to threshold current, produce the 3rd current limliting signal, described the second cut-off current is greater than described the first cut-off current;
Described governor circuit is suitable for producing the gate drive signal of described switching tube and the gate drive signal of described continued flow tube according to clock signal, described the first current limliting signal, described the second current limliting signal and described the 3rd current limliting signal, when receiving described the first current limliting signal, control described switching tube cut-off, continued flow tube conducting, when described clock signal period finishes and receive described the second current limliting signal, keep described switching tube cut-off, continued flow tube conducting, when receiving described the 3rd current limliting signal, control described switching tube conducting, continued flow tube cut-off.
2. the current-limiting circuit of booster converter as claimed in claim 1, is characterized in that, described threshold current is less than or equal to described the second cut-off current.
3. the current-limiting circuit of booster converter as claimed in claim 1, is characterized in that, described governor circuit is rest-set flip-flop;
The reset terminal of described rest-set flip-flop is suitable for inputting described clock signal, the first set end of described rest-set flip-flop is suitable for inputting described the first current limliting signal, the second set end of described rest-set flip-flop is suitable for inputting described the second current limliting signal or described the 3rd current limliting signal, the first output of described rest-set flip-flop is suitable for exporting the gate drive signal of described switching tube, and the second output of described rest-set flip-flop is suitable for exporting the gate drive signal of described continued flow tube.
4. the current-limiting circuit of booster converter as claimed in claim 1, is characterized in that, described governor circuit is also suitable for controlling described switching tube conducting, continued flow tube cut-off when described clock signal period finishes and do not receive described the second current limliting signal.
5. the current-limiting circuit of booster converter as claimed in claim 1, is characterized in that, described switching tube and continued flow tube are metal-oxide-semiconductor.
6. the current-limiting circuit of booster converter as claimed in claim 1, is characterized in that, described switching tube and continued flow tube are IGBT.
7. a current-limiting method for booster converter, described booster converter comprises switching tube and continued flow tube, it is characterized in that, the current-limiting method of described booster converter comprises:
At described switching tube conducting, continued flow tube, between the off period, detect the electric current that flows through described switching tube, when the electric current that flows through described switching tube is more than or equal to the first cut-off current, control described switching tube cut-off, continued flow tube conducting;
When described booster converter work at present end cycle, the electric current of described continued flow tube is flow through in judgement:
If flow through the electric current of described continued flow tube, be less than the second cut-off current, control described switching tube conducting, continued flow tube cut-off, enter the next work period, described the second cut-off current is greater than described the first cut-off current;
If flow through the electric current of described continued flow tube, be more than or equal to described the second cut-off current, keep described switching tube conducting, continued flow tube cut-off, until when flowing through the electric current of described continued flow tube and dropping to threshold current, control described switching tube conducting, continued flow tube cut-off, enter the next work period.
8. the current-limiting method of booster converter as claimed in claim 7, is characterized in that, described threshold current is less than or equal to described the second cut-off current.
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| CN201310743640.7A CN103701312A (en) | 2013-12-29 | 2013-12-29 | Current limiting circuit and method of boost converter |
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| CN201310743640.7A CN103701312A (en) | 2013-12-29 | 2013-12-29 | Current limiting circuit and method of boost converter |
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| CN103701312A true CN103701312A (en) | 2014-04-02 |
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| CN201310743640.7A Pending CN103701312A (en) | 2013-12-29 | 2013-12-29 | Current limiting circuit and method of boost converter |
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