Background technology
Power governor, for example DC-DC converter is used for stable voltage source to various electric systems being provided.(like laptop computer, mobile phone, charger etc.) especially need high efficiency DC-DC converter to the management of battery in the low power-supply device.The switching mode power governor converts input direct voltage to high-frequency voltage, high-frequency output voltage is being carried out filtering and then is converting VD to.Specifically, power governor generally includes a switching device, an output filter and a controller, and switching device and an input dc power potential source (like battery) be alternating to be connected and to break off to give load (like integrated circuit) power supply.Output filter is connected between input voltage source and the load, is made up of inductance and electric capacity, is used for the output of switching device is carried out filtering and then VD is provided.Controller (for example pulse-width modulator or frequency pulse modulator etc.) is controlled the on off state of above-mentioned switching device according to the state of output signal, exports a metastable direct voltage with this.
In such power governor structure,, cause temperature to raise in order to prevent to cause that the input side electric current is excessive under output short-circuit or the circuit overcurrent condition; The overheated device failure that makes perhaps makes its life-span reduce; Usually all can in circuit, add peak current current-limiting circuit part, when transient current was excessive, the peak current current-limiting circuit was partly started working; To turn-off perhaps this peak current current limliting is made it to reduce, thereby play the effect of protecting device for power switching.
Yet above-mentioned current-limiting circuit only is that power governor itself is protected, and in practical application, input power supply (like the USB confession) is needed current-limiting protection equally, is necessary the mean value of input current is carried out the current limliting operation.Current-limiting protection circuit at first will have a current sampling link, and general way is small resistor of series connection or adopts Hall element to obtain current signal.When sample rate current was smaller, these two kinds of sampling methods all were desirable.But when sampling current was bigger, resistance sampling had bigger loss, reduced the efficient of converter, and the Hall element sample volume was bigger, and cost an arm and a leg, and the cost of whole power supply increases.
As shown in Figure 1; It realizes circuit theory diagrams for the input current current limliting of using outer meeting resistance in the existing power regulator circuitry; Power governor comprises input sample resistance 11, parts such as amplifier 12, control circuit 13, drive circuit 14, switching device and filter circuit.Adopt input sample resistance 11 to obtain input current, and its amplification is obtained the current average signal through amplifier 12; Through comparator current average signal and reference signal are compared, then comparative result is input to control circuit 13, when current average signal during greater than reference signal, control circuit 13 stopcock devices are realized the restriction to excessive input current.
But; Adopt this method; Inevitably because the existence of sampling resistor 11; Can be above that produce bigger power loss, square being directly proportional of the resistance size of its numerical values recited and sampling resistor 11 and circuit input current value, and also there is certain direct current quiescent dissipation in detecting amplifier 12 parts.For example, suppose that the circuit input current is 1A, when input sample resistance was 100m Ω, then at this moment the power loss of sampling resistor 11 was approximately 100mW, and obviously it can not satisfy the use of high efficiency application scenario.
In addition, this method need be at the peripheral external sampling resistor of power governor, and parts such as comparator, amplifier, makes that circuit area becomes big, noise effect is also bigger.
Summary of the invention
In view of this, the purpose of this invention is to provide a kind of power governor, to solve big, the inefficient problem of its power loss of implementation method of existing external sampling resistor with the loss-free input current average value current-limiting circuit of power.
Another object of the present invention is to provide input current average value limiting method in a kind of power governor, to solve big, the inefficient problem of its power loss of implementation method of existing external sampling resistor.
For achieving the above object, the present invention provides a kind of power governor, comprises switching device, control circuit; Output filter circuit and input current average value restricting circuits; Control circuit will be imported power source conversion and become high-frequency signal according to a periodic conducting of output voltage feedback signal control switch device and a shutoff, but filter circuit converts high-frequency signal to the output signal of powering load; And export an output voltage feedback signal to control circuit, the input current average value restricting circuits comprises:
The lossless current sampling circuit that comprises a mirror image switch device identical with said switching device type; Be connected with switching device; Cross the transient current of switching device in order to lossless sample streams, obtain and the proportional input sample electric current of electric current that flows through switching device;
Current-voltage conversion circuit is connected with lossless current sampling circuit, in order to the computing of the input sample electric current value of averaging is obtained input current average value, and converts input current average value into first voltage signal;
Average current adjustment circuit; Be connected with control circuit with current-voltage conversion circuit respectively; In order to receiving first voltage signal and one first reference signal, and first voltage signal and first reference signal are compared processing, result exports control circuit to; With the action of control switch device, thus the mean value of restriction input current.
According to the described power governor of preferred embodiment of the present invention, flowing through said switching device is N with the current ratio that flows through the mirror image switch device: 1, and N is not less than 10.
According to the described power governor of preferred embodiment of the present invention, its current-voltage conversion circuit comprises first resistance and first electric capacity, is connected with average matrix current adjustment circuit with lossless current sampling circuit respectively after first resistance and the first electric capacity parallel connection.
According to the described power governor of preferred embodiment of the present invention; Its input current average value restricting circuits also comprises a current amplification circuit; Current amplification circuit is connected with current-voltage conversion circuit with lossless current sampling circuit respectively, in order to the input sample electric current is carried out processing and amplifying.
According to the described power governor of preferred embodiment of the present invention; Its current amplification circuit comprises an amplifier and a transistor, and amplifier amplifies the input sample electric current and the electric current that flows through said switching device when guaranteeing to flow out transistorized input sample electric current with the switching device conducting is directly proportional.
According to the described power governor of preferred embodiment of the present invention; Its average current adjustment circuit comprises a comparator; Comparator obtains a current limliting signal in order to first voltage signal and one first reference signal are compared; When first voltage signal during greater than first reference signal, the action of current limliting Signal-controlled switch device is with the mean value of restriction input current.
According to the described power governor of preferred embodiment of the present invention, its average current adjustment circuit comprises an amplifier, and amplifier is in order to compare first voltage signal and one first reference signal and to amplify and produce current error signal.
According to the described power governor of preferred embodiment of the present invention, its control circuit further comprises the output voltage feedback loop, and this output voltage feedback loop relatively produces output error signal with voltage feedback signal and one second reference signal,
When input current average value surpassed the input current average value threshold value, when promptly first voltage signal was greater than first reference signal, control circuit was according to current error signal stopcock device, with the mean value of restriction input current;
When input current average value does not surpass the input current average value threshold value; When promptly first voltage signal is less than first reference signal; Control circuit is adjusted the conducting and the turn-off time of switching device according to the action of output error signal control switch device, and regulates the output signal with this.
The present invention also provides input current average value limiting method in a kind of power governor, may further comprise the steps:
(1) adopts the image current method that the electric current that flows through switching device is carried out lossless sampling, obtain the input sample electric current;
(2) through the current-voltage conversion circuit to the value of the averaging computing of input sample electric current and be converted into first voltage signal;
(3) through average current adjustment circuit first voltage signal and one first reference signal are compared; Judge that whether first voltage signal is greater than first reference signal; If first voltage signal is greater than first reference signal; Output current limiting signal to control circuit stopcock device is with restriction input average current; Otherwise, return step (1).
According to input current average value limiting method in the preferred embodiment power governor of the present invention, above-mentioned step (2) also comprises before: through current amplification circuit the input sample electric current is carried out processing and amplifying.
The present invention provides input current average value limiting method in a kind of power governor again, it is characterized in that, may further comprise the steps:
(1) adopts the image current method that the electric current that flows through switching device is carried out lossless sampling, obtain the input sample electric current;
(2) through the current-voltage conversion circuit to the value of the averaging computing of input sample electric current and be converted into first voltage signal;
(3) average current adjustment circuit is with first voltage signal and one first reference signal compares and amplification obtains a current error signal; The output voltage feedback circuit compares generation one output error signal with the voltage feedback signal and one second reference signal of power governor output.
(4) judge that current error signal is whether less than output error signal: if current error signal is less than output error signal, said control circuit is according to current error signal stopcock device, with the mean value of restriction input current; Otherwise greater than output error signal, said control circuit is adjusted the conducting and the turn-off time of switching device according to the action of output error signal control switch device, and regulates the output signal with this as if current error signal.
According to input current average value limiting method in the preferred embodiment power governor of the present invention, above-mentioned step (2) also comprises before: through current amplification circuit the input sample electric current is carried out processing and amplifying.
Adopt the realization circuit and the control method thereof of power governor of the present invention, can realize the loss-free input current average value restriction of power, realize current-limiting protection effect input source.Simultaneously can this input current average value restricting circuits be integrated in power governor inside, save peripheral circuit, power consumption reduces, and efficient improves, simplified circuit design, the increase of entire circuit reliability.
Embodiment
Below in conjunction with accompanying drawing the preferred embodiments of the present invention are described in detail.The purpose that the present invention chooses these embodiment is not that scope of the present invention is limited to these embodiment, but makes those of ordinary skills can better understand and use the present invention.
With reference to figure 2A to Fig. 2 B, it is respectively theory diagram and the working waveform figure thereof of first embodiment of power governor of the present invention.This power governor comprises DC/DC change-over circuit 200 and input current average value restricting circuits 201, and DC/DC change-over circuit 200 comprises switching device, control circuit (PWMControl) and output filter circuit.Wherein, switching device is a transistor 21, and transistor 21 is mosfet transistors.Filter circuit comprises outputting inductance L, output capacitance C
OutDC/DC change-over circuit 200 also comprises an output resistor voltage divider network, and the output resistor voltage divider network comprises two feedback resistance R
Fb1, R
Fb2FB is an output voltage feedback signal, and control circuit comes oxide-semiconductor control transistors 21 periodic conducting and shutoffs according to output voltage feedback signal FB, to produce high-frequency signal, passes through the outputting inductance L and the output capacitance C of filter circuit then
OutCarry out filtering, supply power to output loading thereby export a direct current voltage.
Above-mentioned DC/DC change-over circuit 200 is a prior art, repeats no more at this.Below the circuit element annexation and the course of work in the input current average value restricting circuits 201 of the present invention are elaborated.
Input current average value restricting circuits 201 comprises lossless current sampling circuit 202, current-voltage conversion circuit 203 and average matrix current adjustment circuit 204.
Lossless current sampling circuit 202 is by forming with switching device (being transistor 21) the mirror image switch device that type is identical (being mirrored transistor 22); Select mosfet transistor in this embodiment for use; Flowing through transistor 21 is N with the ratio relation that flows through both electric currents of mirrored transistor 22: 1; In general, N is greater than 10, and the electric current of mirrored transistor 22 is than the electric current that flows through transistor 21 little at least 90% like this.In order further to reduce loss, the general value of N is more than 1000.
Shown in Fig. 2 B, it is I that the input on the mirrored transistor 22 detects electric current
SEN, the electric current of transistor 21 is I
S, the current average that let flow is crossed outputting inductance L is I
p, the conducting duty ratio of transistor 21 is D, transistor 21 is N with the ratio of mirrored transistor 22.
The current value of outputting inductance L is I
L, its mean value is I
p, then the current waveform on the transistor 21 is the square wave of duty ratio D, its input current average value I
InFor:
I
in=I
P×D (1)
The input sample electric current that then flows through mirrored transistor 22 is I
SEN, its average current value I
AveShown in the following formula (2):
Current-voltage conversion circuit 203 is made up of first resistance 24 and first electric capacity 25, in order to the input sample electric current I
SENCarry out Filtering Processing, and be converted into the first voltage signal V at node 23 places
LimIf the time constant filter that first resistance 24 and first electric capacity 25 are formed is much larger than the switch periods of transistor 21, then V
LimWaveform be the voltage near direct current, V
LimMean value V
Lim_aveShown in the following formula of its numerical values recited (3):
R wherein
LimIt is the resistance value of first resistance 24.
Average current adjustment circuit 204 comprises a comparator 26, and its normal phase input end connects one first reference signal V
Ref1, inverting input connected node 23, i.e. the common node of mirrored transistor 22, first resistance 24 and first electric capacity 25, the current limliting signal of the output of comparator 26 is connected to the control circuit part.
Comparator 26 is with the first voltage signal V
LimWith the first reference signal V
Ref1Compare, the control circuit part is according to the on off state of output result (current limliting signal) oxide-semiconductor control transistors 21 of comparator 26.
As voltage V
LimEnough hour of ripple, if V
Lim_aveNumerical value greater than V
Ref1, then control circuit part oxide-semiconductor control transistors 21 is turn-offed, thereby input current average value threshold value I
In_limShown in the following formula of numerical values recited (4):
The input current average value I that promptly obtains when sampling
InGreater than input current average value threshold value I
In_lim, comparator 26 output current limiting signals are given control circuit, and control circuit part control switch device is that transistor 21 turn-offs, thereby reaches the effect of restriction input average current.
In the preferred embodiment, switching device is that transistor 21 adopts mosfet transistor in this embodiment, and those of ordinary skills can know, and the switching device of other types also can be applied in the present embodiment such as bipolar transistor etc.
With reference to figure 3, be the theory diagram of power governor second embodiment of the present invention.For ease of explanation, the assembly identical with Fig. 2 A is the primary clustering symbol of continuing to use among Fig. 2 among Fig. 3.In the present embodiment; Power governor comprises existing DC/DC change-over circuit 200 and input current average value restricting circuits 301; Wherein, Input current average value restricting circuits 301 comprises lossless current sampling circuit 302, current amplification circuit 303, current-voltage conversion circuit 304 and average matrix current adjustment circuit 305.
Lossless current sampling circuit 302 is by forming with switching device (being transistor 21) the mirror image switch device that type is identical (comprising mirrored transistor 22,33), inverter 31, transistor 32.Wherein mirrored transistor 33 can be used as the image current sampling; Select mosfet transistor in this embodiment for use; Mirrored transistor 33 is identical with mirrored transistor 22 sizes; Both ratio relations of transistor 21 and mirrored transistor 33 are N: 1, and the General N value is greater than 10, and it is few more than 90% to make the current ratio that flows through mirrored transistor 33 flow through the electric current of transistor 21.In order further to reduce loss, N value value is greater than 1000.
Inverter 31 guarantees when transistor 21 turn-offs, do not have voltage to be added on the mirrored transistor 33 with transistor 32, so when transistor 21 turn-offs, do not have the input sample electric current I
SENFlow out transistor 35.
Current amplification circuit 303 comprises amplifier 34 and transistor 35, and it is used to guarantee to flow out the input sample electric current I of transistor 35
SENElectric current I when being transistor 21 conductings with switching device
SBe directly proportional.
Current-voltage conversion circuit 304 comprises first resistance 24 and first electric capacity 25, and it forms a RC filter circuit, in order to the input sample electric current I
SENAverage processing, and convert this average current signal the first voltage signal V of node 23 places into
LimAverage current adjustment circuit 305 comprises comparator 26, and its in-phase input end connects the first reference signal V
Ref1, inverting input connected node 23, the output of comparator 26 connects the control circuit part of transistor 21; Control circuit is according to the on off state of output result (current limliting signal) oxide-semiconductor control transistors 21 of comparator 26.As detected input current average value I
InGreater than input current average value threshold value I
In_limThe time, control circuit turn-offs transistor 21, with restriction input current average value I
In
Adopt this method, lossless current sampling circuit, current amplification circuit, current-voltage conversion circuit and average matrix current adjustment circuit are integrated in chip internal, therefore do not need again external extra chip periphery circuit; Such as parts such as sampling resistors, avoided extra power loss, improved the service efficiency of power governor; And avoided the influence of external noise; Circuit stability strengthens, and has also simplified the design of circuit simultaneously, has more practicality.
With reference to figure 4, the comparator 26 among Fig. 2 A and Fig. 3 also can substitute with an amplifier 41, and amplifier 41 inverting inputs are connected to node 23, receives detected input current average value signal V
Lim, in-phase input end connects the first reference signal V
Ref1, it is output as current error signal V
Ier, be connected to the inverting input of control circuit comparator 46 through diode 45.Output voltage feeds back to routing amplifier 42 and provides, and amplifier 42 receives the output voltage feedback signal FB and the second reference signal V
Ref2, and both are compared, thereby produce an output error signal V
Oer, be connected to the inverting input of comparator 46 through diode 44.Diode 44 and 45 is chosen output error signal V then
OerWith current error signal V
IerIn lower signal, through comparator 46 and triangular signal V
RampThereby the operating state of comparison control switch transistor 21.
As input current average value I
InSurpass input current average value threshold value I
In_limThe time, i.e. the first voltage signal V
LimGreater than the first reference signal V
Ref1The time, current error signal V
IerThe control switch device is the action of transistor 21, with the restriction input current average value; As input average current mean value I
InDo not surpass input current average value threshold value I
In_limThe time, i.e. the first voltage signal V
LimLess than the first reference signal V
Ref1The time, output error signal V
OerThe control switch device is the action of transistor 21, adjusts the conducting and the turn-off time of transistor 21, and regulates output voltage with this.
Reading on the basis of this specification, those of ordinary skill in the art is to be understood that some counterpart in Fig. 2 A, Fig. 3 and the current limit circuit shown in Figure 4 can exchange use, for example sampling among Fig. 2 A, Fig. 3 and amplification circuits etc.; In addition, be not limited to type shown in the accompanying drawing and type combination according to spendable transistorized type in the above embodiment of the present invention.
With reference to figure 5, input current average value limiting method in a kind of power governor may further comprise the steps:
S11: adopt the image current method that the electric current that flows through switching device is carried out lossless sampling, obtain the input sample electric current;
S12: through the current-voltage conversion circuit to the value of the averaging computing of input sample electric current and be converted into first voltage signal;
S13: first voltage signal and one first reference signal are compared through average current adjustment circuit; Judge that whether first voltage signal is greater than first reference signal; If first voltage signal is greater than first reference signal; Output current limiting signal to control circuit stopcock device is with restriction input average current (S14); Otherwise, return step S11.
Wherein, also comprise before the step S12: the input sample electric current is carried out processing and amplifying through current amplification circuit.
With reference to figure 6, input current average value limiting method in a kind of power governor may further comprise the steps:
S21: adopt the image current method that the electric current that flows through switching device is carried out lossless sampling, obtain the input sample electric current;
S22: through the current-voltage conversion circuit to the value of the averaging computing of input sample electric current and be converted into first voltage signal;
S23: average current adjustment circuit is with first voltage signal and one first reference signal compares and amplification obtains a current error signal; The output voltage feedback circuit compares generation one output error signal with the output voltage feedback signal and second reference signal.
S24: judge that current error signal is whether less than output error signal: if current error signal is less than output error signal, said control circuit is according to current error signal stopcock device, with the mean value (S25) of restriction input current; Otherwise greater than output error signal, said control circuit is adjusted the conducting and the turn-off time of switching device according to the action of output error signal control switch device as if current error signal, and regulates output signal (S26) with this.
Wherein, also comprise before the step S22: the input sample electric current is carried out processing and amplifying through current amplification circuit.
The above-mentioned current error signal and the magnitude relationship of output error signal obtain according to the comparative result of first voltage signal and first reference signal; When input current average value surpasses the input current average value threshold value; When promptly first voltage signal was greater than first reference signal, current error signal was less than output error signal; When input current average value did not surpass the input current average value threshold value, when promptly first voltage signal was less than first reference signal, current error signal was greater than output error signal.
More than structure and control method according to power governor of the preferred embodiments of the present invention and current-limiting protection circuit have wherein been carried out detailed description, those of ordinary skills can know other technologies or structure and circuit layout, element etc. in view of the above by inference and all can be applicable to said embodiment.For example, what adopt in the above-described embodiments is pulse width regulator, but other modulation scheme is suitable for too, modulates like frequency pulse.In addition, the buck converter topology structure in the foregoing description also can replace with other power governor topological structure such as boost converter, type of voltage step-up, radio frequency output amplifier.
As indicated above according to embodiments of the invention, these embodiment do not have all details of detailed descriptionthe, do not limit this invention yet and are merely described specific embodiment.Obviously, according to above description, can do a lot of modifications and variation.These embodiment are chosen and specifically described to this specification, is in order to explain principle of the present invention and practical application better, thereby person skilled can utilize the present invention and the modification on basis of the present invention to use well under making.The present invention only receives the restriction of claims and four corner and equivalent.