CN202455267U

CN202455267U - Power supply circuit

Info

Publication number: CN202455267U
Application number: CN2011202394067U
Authority: CN
Inventors: 韦雄观; 黄建宁; 王克军
Original assignee: XI'AN TIANZHAO WEICHENG ELECTRIC CO Ltd
Current assignee: XI'AN TIANZHAO WEICHENG ELECTRIC CO Ltd
Priority date: 2011-07-08
Filing date: 2011-07-08
Publication date: 2012-09-26
Anticipated expiration: 2021-07-08

Abstract

The present utility model discloses a power supply circuit. In the power supply circuit, a first end of an adjustable parameter constant current source is connected with a first end of a voltage adjusting circuit, a second end is connected with a first end of a filter circuit, a control end of a voltage adjusting circuit and a first end of a feedback amplification circuit; a second end of the voltage adjusting circuit is connected with a first end of an output voltage sampling circuit, the control end is also connected with the first end of the feedback amplification circuit and the first end of the filtering circuit; the first end of the feedback amplification circuit is connected with the first end of the filtering circuit, a second end is connected with a first end of a temperature compensation and control circuit, and a control end is connected with a second end of the output voltage sampling circuit; a second end of the temperature compensation and control circuit, a second end of the filtering circuit, and a third end of the output voltage sampling circuit are connected with the ground; input voltage can be input to the first end of the adjustable parameter constant current source and the first end of the voltage adjusting circuit; output voltage is output from the second end of the voltage adjusting circuit; thus high temperature resistant, high voltage resistant performances and large power can be realized.

Description

Power circuit

Technical field

The utility model relates to power technique fields, relates in particular to power circuit.

Background technology

Along with exploration of oil and gas field, exploitation scope are further expanded to adverse circumstances such as underground deep layer district, sea, beach and deep-seas; In order to accomplish the collection of exploration, completion, exploitation and oil reservoir data accurately and efficiently, all new challenge and requirement will be proposed to modular design and the overall performance that is operated in the downhole instrument in the extreme environments such as high temperature, high pressure, deep-etching.Wherein, High-quality high temperature resistant power module of voltage regulation; Realize the basis of high performance device for subsurface measuring and data acquisition system often; It not only directly has influence on life-span, precision, sensitivity and the reliability of equipment, is also directly determining production cost, the function of instrument integrated and to working environment adaptability---such as supply power voltage and temperature range or the like.Be the raising operating efficiency that reduces cost, when multi-parameter is logged well, need throw in the instrument string of multiple different capacity and supply power voltage usually simultaneously.At this moment, if these instruments are to connect through cable, then the most simply be exactly to adopt single-core cable and single voltage source to come to supply power to all appts; If powered battery generally all adopts the cascaded structure of multiple batteries to reach certain battery capacity and voltage amplitude (the battery series connection is more suitable for the tubular column structure of downhole instrument than parallel connection); No matter be which kind of situation, all require the supply voltage of all appts, must be able to bear power supply the highest in instrument input, add extra battery or supply voltage (being used to compensate the voltage fluctuation that causes because of cell decay or long cable loss).

Therefore, as the high temperature power module of desirable high-end downhole instrument, require below preferably satisfying simultaneously: input voltage range is big, and output voltage is to the good stability of input fluctuation; Operating temperature range is big, and the high temperature drift is low; Ripple is little, and power output is big, to the good stability of load; Preferably can realize low pressure differential, and reduce power consumption as far as possible and raise the efficiency.

Fig. 1 a and Fig. 1 b are traditional transistor series voltage stabilizing circuit figure, adopt the linear voltage stabilization structure to realize low ripple and low pressure differential.Fig. 1 b is the improvement circuit of Fig. 1 a, adopts operational amplifier to realize the feedback error amplifying circuit.These two kinds of circuit structures all are to adopt high-power pipe to realize big dynamic range input and high-power output, and adopt the negative temperature characteristic of triode be knot (or diode) to realize the temperature-compensating under the high temperature, but the subject matter of its circuit is:

Voltage fluctuation to input is relatively more responsive, and input voltage range is limited.Because input voltage fluctuation directly influences the voltage at biasing resistor R3 two ends and the electric current of adjustment pipe, can cause output voltage to fluctuate with the variation of input voltage, so can't be applicable to big dynamic adjusting range.

Parameter to temperature-compensating is unadjustable, and accuracy is limited.Its compensating circuit is that hypothesis compensation pipe T3 can have on all four temperature characterisitic with feedback amplifier tube T2 in very wide temperature range; Perhaps the forward temperature of diode D1, D2, D3 is floated characteristic and reverse temperature to float characteristic opposite fully, thereby reaches the effect of cancelling out each other; But generally be difficult to find fully the pipe of coupling, circuit does not consider that the temperature of other devices floats and parameter discrete property yet, is difficult to hot environment is changed and device discreteness realization fine compensation.

Adopt integrated operational amplifier to do Error Feedback and amplify, can improve output adjustment sensitivity though normal temperature is worked down, unadjustable to the parameter of temperature-compensating, its accuracy is still limited.In addition, be limited to present technological level, the input voltage of integrated transporting discharging generally can not surpass 30V ~ 40V, can't bear the high pressure input up to last hectovolt; All between-40 ℃ to 85 ℃, not only cost was expensive when temperature was higher than 85 ℃ ~ 125 ℃ basically for the hot operation scope that can adapt to, and temperature drift is also very serious, and temperature will be difficult to steady operation greater than 150 ℃.

The utility model content

The utility model embodiment provides a kind of power circuit, in order to reduce the input voltage fluctuation susceptibility, adapts to large-scale input voltage, and makes the parameter scalable of temperature-compensating, and accuracy improves, and this power circuit comprises:

Adjustable parameter constant-current source, voltage-regulating circuit, feedback amplifier, temperature-compensating and control circuit, output voltage sampling circuit, filter circuit; Wherein:

First end of adjustable parameter constant-current source links to each other with first end of voltage-regulating circuit; Second end of adjustable parameter constant-current source links to each other with the control end of first end of filter circuit, voltage-regulating circuit, first end of feedback amplifier;

Second end of voltage-regulating circuit links to each other with first end of output voltage sampling circuit; The control end of voltage-regulating circuit also links to each other with first end of feedback amplifier, first end of filter circuit;

First end of feedback amplifier also links to each other with first end of filter circuit; Second end of feedback amplifier links to each other with first end of control circuit with temperature-compensating; The control end of feedback amplifier links to each other with second end of output voltage sampling circuit;

The 3rd end ground connection of second end of temperature-compensating and control circuit, second end of filter circuit, output voltage sampling circuit;

Input voltage inputs to first end of adjustable parameter constant-current source, first end of voltage-regulating circuit; Output voltage is by second end output of voltage-regulating circuit;

The adjustable parameter constant-current source is used for driving voltage adjustment circuit, feedback amplifier, temperature-compensating and control circuit; Voltage-regulating circuit is used to adjust voltage; Feedback amplifier is used for output error is fed back amplification; Temperature-compensating and control circuit are used to produce temperature variant reference voltage, with compensate for temperature drift; Output voltage sampling circuit is used for output voltage is carried out dividing potential drop, generates feedback sample voltage and offers feedback amplifier; Filter circuit is used for filtering.

Among the embodiment, the adjustable parameter constant-current source comprises:

PN junction type fet JFET and adjustable resistance R0; Wherein:

The drain electrode of JFET is first end of adjustable parameter constant-current source; The grid of JFET links to each other with second end of adjustable resistance R0, and second end of the grid of JFET and adjustable resistance R0 is second end of adjustable parameter constant-current source; The source electrode of JFET links to each other with first end of adjustable resistance R0.

Triode T1, T2, fixed resistance R2 and adjustable resistance R0; Wherein: triode T1, T2 are the NPN pipe;

The collector electrode of triode T1 links to each other with first end of fixed resistance R2, and first end of the collector electrode of triode T1 and fixed resistance R2 is first end of adjustable parameter constant-current source; The base stage of triode T1 links to each other with second end of fixed resistance R2, the collector electrode of triode T2; The emitter of triode T1 links to each other with the base stage of triode T2, first end of adjustable resistance R0;

Second end of fixed resistance R2 also links to each other with the collector electrode of triode T2;

The base stage of triode T2 also links to each other with first end of adjustable resistance R0; The emitter of triode T2 links to each other with second end of adjustable resistance R0, and second end of the emitter of triode T2 and adjustable resistance R0 is second end of adjustable parameter constant-current source.

Among the embodiment, voltage-regulating circuit comprises triode T1; Triode T1 is the NPN pipe; The current collection of triode T1 is first end of voltage-regulating circuit very; The emission of triode T1 is second end of voltage-regulating circuit very; The base stage of triode T1 is the control end of voltage-regulating circuit.

Among the embodiment, voltage-regulating circuit comprises triode T1, T3 and fixed resistance R4;

Triode T3 is the PNP pipe; The emission of triode T3 is first end of voltage-regulating circuit very; The current collection of triode T3 is second end of voltage-regulating circuit very; The base stage of triode T3 links to each other with the collector electrode of triode T1;

Triode T1 is the NPN pipe; The emitter of triode T1 links to each other with first end of fixed resistance R4; The base stage of triode T1 is the control end of voltage-regulating circuit;

The second end ground connection of fixed resistance R4.

Among the embodiment, voltage-regulating circuit comprises triode T1, T3;

Triode T3 is the PNP pipe; The emission of triode T3 is first end of voltage-regulating circuit very; The collector electrode of triode T3 links to each other with the emitter of triode T1, second end that is emitted as voltage-regulating circuit of the collector electrode of triode T3 and triode T1; The base stage of triode T3 links to each other with the collector electrode of triode T1;

Triode T1 is the NPN pipe; The base stage of triode T1 is the control end of voltage-regulating circuit.

Among the embodiment, feedback amplifier comprises triode T2; Triode T2 is the NPN pipe; The current collection of triode T2 is first end of feedback amplifier very; The emission of triode T2 is second end of feedback amplifier very; The base stage of triode T2 is the control end of feedback amplifier.

Among the embodiment, temperature-compensating and control circuit comprise: the serial or parallel connection circuit that adjustable RTD, fixed resistance, thermistor, thermal diode one of them or combination in any form.

Among the embodiment, output voltage sampling circuit comprises: fixed resistance R1, adjustable resistance R2; First end of fixed resistance R1 is first end of output voltage sampling circuit; Second end of fixed resistance R1 links to each other with first end of adjustable resistance R2, and second end of fixed resistance R1 and first end of adjustable resistance R2 are second end of output voltage sampling circuit; Second end of adjustable resistance R2 is the 3rd end of output voltage sampling circuit.

Among the embodiment, filter circuit comprises capacitor C 1; First end of capacitor C 1 is first end of filter circuit; Second end of capacitor C 1 is second end of filter circuit.

The power circuit of the utility model embodiment still all can form the negative feedback adjustment to the drift of temperature to the fluctuation of output voltage, thereby can reach the effect of auto thermal compensation and automatic voltage regulation simultaneously, realizes high temperature resistant, high voltage withstanding and high-power easily; And only need the suitably parameter in design adjustable constant-flow source, just can satisfy big input voltage range, wide temperature compensation range and good output stability simultaneously; The parameter regulation of temperature-compensating has good independence and flexibility, can realize the accurate correction of various different temperature coefficients easily.The circuit construction of electric power of the utility model embodiment is simple, interface is clear; Be easy to modularized design and optimization; Can be applicable to the oil reservoir logging field; Adapt to the down-hole high temperature stabilized voltage power supply design of wide input range, be particularly suitable for big under the hot environment to the input voltage fluctuation scope, power output is high, good stability, the low application scenario of temperature drift; Can also be applied to widely and in the electronic circuit input fluctuation senser big, that temperature drift is big carried out voltage and temperature-compensating.

Description of drawings

In order to be illustrated more clearly in the utility model embodiment or technical scheme of the prior art; To do to introduce simply to the accompanying drawing of required use in embodiment or the description of the Prior Art below; Obviously, the accompanying drawing in describing below only is some embodiment of the utility model, for those of ordinary skills; Under the prerequisite of not paying creative work property, can also obtain other accompanying drawing according to these accompanying drawings.In the accompanying drawings:

Fig. 1 a is a kind of traditional transistor series voltage stabilizing circuit figure in the background technology;

Fig. 1 b is another kind of traditional transistor series voltage stabilizing circuit figure in the background technology;

Fig. 2 a is its overall structure block diagram of power circuit among the utility model embodiment;

Fig. 2 b is a kind of schematic diagram that adopts all-transistor circuity to realize among the utility model embodiment;

Fig. 3 a is based on the structural representation of the adjustable parameter constant-current source of JFET among the utility model embodiment;

Fig. 3 b is based on the structural representation of transistorized adjustable parameter constant-current source among the utility model embodiment;

Fig. 4 a to Fig. 4 d is four kinds of topology example figure of temperature-compensating and control circuit among the utility model embodiment;

Fig. 5 a-1 is the examples of circuits figure that linear temperature senser such as temperature-compensating and control circuit employing Pt RTD is realized linear compensation among the utility model embodiment;

Fig. 5 a-2 is the circuit temperature characteristic exemplary plot that linear temperature senser such as temperature-compensating and control circuit employing Pt RTD is realized linear compensations among the utility model embodiment;

Fig. 5 b-1 is the examples of circuits figure that temperature-compensating and control circuit limit the almost compensation of slope variation and maximum compensation range among the utility model embodiment;

Fig. 5 b-2 is the circuit temperature characteristic exemplary plot that temperature-compensating and control circuit limit the almost compensation of slope variation and maximum compensation range among the utility model embodiment;

Fig. 5 c-1 is the examples of circuits figure that temperature-compensating and control circuit limit the standard 2 rank compensation of amplitude of variation and maximum compensation range among the utility model embodiment;

Fig. 5 c-2 is the circuit temperature characteristic exemplary plot that temperature-compensating and control circuit limit the standard 2 rank compensation of amplitude of variation and maximum compensation range among the utility model embodiment;

Fig. 5 d-1 is the examples of circuits figure that temperature-compensating and control circuit limit the 2 rank compensation of amplitude of variation and maximum compensation range among the utility model embodiment;

Fig. 5 d-2 is the circuit temperature characteristic exemplary plot that temperature-compensating and control circuit limit the 2 rank compensation of amplitude of variation and maximum compensation range among the utility model embodiment;

Fig. 5 e-1 is that temperature-compensating and control circuit adopt the more examples of circuits figure of the thermistor of high-order among the utility model embodiment;

Fig. 5 e-2 is that temperature-compensating and control circuit adopt the more circuit temperature characteristic exemplary plot of the thermistor of high-order among the utility model embodiment;

Fig. 6 a adopts NPN pipe T1 to setover over the ground to drive the sketch map that PNP pipe T3 makes voltage-regulating circuit among the utility model embodiment;

Fig. 6 b adopts NPN pipe T1 that output is setovered to drive the sketch map that PNP (or IGBT) pipe T3 makes voltage-regulating circuit among the utility model embodiment;

Fig. 7 a is the traditional circuit sketch map that experimentizes among the utility model embodiment and compare;

Fig. 7 b is the utility model instantiation circuit diagram that experimentizes among the utility model embodiment and compare.

Embodiment

For the purpose, technical scheme and the advantage that make the utility model embodiment is clearer, the utility model embodiment is explained further details below in conjunction with accompanying drawing.At this, illustrative examples of the utility model and explanation thereof are used to explain the utility model, but not as the qualification to the utility model.

The purpose of the utility model embodiment is a kind of power circuit that can overcome the problems referred to above of design, can adapt to needs input ranges such as downhole instrument or watch-dog big (up to dozens or even hundreds of volt), output stability is good, power is high, the high temperature drift is low applied environment.The power circuit of the utility model embodiment has that circuit is simple, the easy advantage such as flexible, with low cost of parameter adjustment; Not only can be applicable to the hydrocarbon well logging field, can also be applied to widely and in the electronic circuit input fluctuation senser big, that temperature drift is big carried out voltage and temperature-compensating.

For achieving the above object; The utility model embodiment provides a kind of power circuit; Its overall structure block diagram mainly comprises referring to Fig. 2 a: adjustable parameter constant-current source, voltage-regulating circuit, feedback amplifier, temperature-compensating and control circuit, output voltage sampling circuit, filter circuit.Wherein:

First end 11 of adjustable parameter constant-current source links to each other with first end 21 of voltage-regulating circuit; First end 31 of second end 12 of adjustable parameter constant-current source and filter circuit, the control end 23 of voltage-regulating circuit, first end 41 of feedback amplifier link to each other;

Second end 22 of voltage-regulating circuit links to each other with first end 51 of output voltage sampling circuit; The control end 23 of voltage-regulating circuit also links to each other with first end 41 of feedback amplifier, first end 31 of filter circuit;

First end 41 of feedback amplifier also links to each other with first end 31 of filter circuit; Second end 42 of feedback amplifier links to each other with first end 61 of control circuit with temperature-compensating; The control end 43 of feedback amplifier links to each other with second end 52 of output voltage sampling circuit;

Second end 62 of second end 62 of temperature-compensating and control circuit, filter circuit, the 3rd end 53 ground connection of output voltage sampling circuit;

Input voltage vin inputs to first end 11 of adjustable parameter constant-current source, first end 21 of voltage-regulating circuit; Output voltage V out is by second end, 22 outputs of voltage-regulating circuit;

The adjustable parameter constant-current source is used for driving voltage adjustment circuit, feedback amplifier, temperature-compensating and control circuit; Voltage-regulating circuit is used to adjust voltage; Feedback amplifier is used for output error is fed back amplification; Temperature-compensating and control circuit are used to produce temperature variant reference voltage V ref, with compensate for temperature drift; Output voltage sampling circuit is used for output voltage V out is carried out dividing potential drop, generates feedback sample voltage and offers feedback amplifier; Filter circuit is used for filtering.

The power circuit of the utility model embodiment can adopt incorporate overall height temperature transistor arrangement to add temperature-sensing element (device) such as RTD (Resistance Temperature Detector; Resistance temperature detector) method of doing the high temperature compensation realizes; Its concrete implementation structure can have various ways, illustrates respectively below.

Among the embodiment, voltage-regulating circuit can comprise triode T1; Triode T1 is the NPN pipe; The current collection of triode T1 is first end of voltage-regulating circuit very; The emission of triode T1 is second end of voltage-regulating circuit very; The base stage of triode T1 is the control end of voltage-regulating circuit.

Among the embodiment, feedback amplifier can comprise triode T2; Triode T2 is the NPN pipe; The current collection of triode T2 is first end of feedback amplifier very; The emission of triode T2 is second end of feedback amplifier very; The base stage of triode T2 is the control end of feedback amplifier.

Among the embodiment, output voltage sampling circuit can comprise: fixed resistance R1, adjustable resistance R2; First end of fixed resistance R1 is first end of output voltage sampling circuit; Second end of fixed resistance R1 links to each other with first end of adjustable resistance R2, and second end of fixed resistance R1 and first end of adjustable resistance R2 are second end of output voltage sampling circuit; Second end of adjustable resistance R2 is the 3rd end of output voltage sampling circuit.

Among the embodiment, filter circuit can comprise capacitor C 1; First end of capacitor C 1 is first end of filter circuit; Second end of capacitor C 1 is second end of filter circuit.

Fig. 2 b is the schematic diagram that a kind of most typical employing all-transistor circuity that the structured flowchart according to Fig. 2 a provides is realized.Among Fig. 2 b; I0 is the adjustable parameter constant-current source; Its parameter can adopt resistance or temperature-sensing element (device) such as RTD to regulate; I0=I1+I2, I0 are used for driving triode T1, T2 and temperature-compensating and control circuit simultaneously, and temperature-compensating among Fig. 2 b and control circuit adopt thermistor Rt to make temperature drift compensation and use; Rt is temperature variant RTD, and the electric current I 2 (changing along with the variation of I0) that flows through will produce temperature variant reference voltage V ref=Rt*I2, as the fine compensation of temperature drift; Fixed resistance R1 and adjustable resistance R2 generate feedback sample voltage Vs=Vout*R2/ (R1+R2) to the dividing potential drop of output voltage V out; The R1 here, R2 are used to regulate the size of output voltage; Divider resistance also can adopt temperature-sensing element (device) RTD and Rt to constitute temperature-compensation circuit together jointly; Feedback error Vbe=Vs – Vref (Vbe:Base to emitter drop, base-emitter voltage drop).

The advantage of circuit is shown in Fig. 2 b: utilize T2 that output error is fed back amplification, and adopt adjustable parameter constant-current source driving RTD to produce temperature variant reference voltage V ref, in order to compensate for temperature drift, improve the precision and the temperature stability of adjustment; Adopt the adjustable parameter constant-current source to drive the biasing circuit of triode T1, biasing fluctuation and output that the elimination input voltage fluctuation causes change; Adopt the base stage of 1 couple of T1 of capacitor C to carry out filtering, not only can reduce circuit noise and AC ripple, can also play the function of soft start protection.

The withstand voltage scope of the input of circuit shown in Fig. 2 b, power output, output voltage depend on selected triode T1, T2 and divider resistance R1, R2, can select flexibly as required.Particularly, T1, T2 also can adopt the Darlington transistor Darlington transistor of PNP and NPN various combination (comprise to), to improve the power and the sensitivity of adjustment.

Structure with circuit shown in Fig. 2 b is an example below, discusses voltage stabilizing and the temperature-compensating process of the utility model embodiment in detail, so that its advantage is had more deeply understanding:

(1), output Vout increase==Vs increases==Vbe increases==T2 conducting, I2 increase==I1 reduces, T1 by==output Vout reduces; Be junction voltage Vbe=Vp (Positive Voltage, positive voltage) when its stationary value is only adjusted balance with T2 is relevant.

(2), the adjustment process that reduces of Vout is similar, the be junction voltage Vbe=Vp during only with T2 adjustment balance is relevant for its stationary value.

(3), input Vin changes, or temperature t raises and causes that T1 changes, or load change==output Vout changes==constant-current source I0 do not receive variable effect==circuit is unaffected to the above-mentioned adjustment process of output voltage V out.

(4), temperature t raises==the be knot conducting of T2 accelerates==during T2 adjustment balance the voltage Vbe=Vp of be knot reduce==stable output Vout reduces, its minimizing amplitude is relevant with the temperature characterisitic of T2.

(5), temperature t raises==thermistor Rt increases==reference voltage V ref=I2*Rt increases==the be knot of T2 because of the negative feedback deflection by==regulated output voltage Vout increases, its increase amplitude and I2 (I0 just) and Rt's is big or small closely related.

(6), above-mentioned (4), (5) are to carry out toward opposite direction to the change of temperature; Because Vref=I2*Rt=(I0 – I1) * Rt ≈ I0*Rt; The amplitude of Vref adjustment receives the influence of I0, as long as select suitable I0 and Rt---such as, floating the junction voltage Vbe variable quantity that causes because of temperature when supposing the T2 balance is △ Vbe; Suppose that again it is △ Rt that temperature is floated the Rt resistance change that causes, then through just letting them that Influence of Temperature is cancelled out each other according to following formula adjustment constant-current source I0:

I0=△ Vbe/ △ Rt (formula 1)

That is: compare with traditional circuit diagram 1a, Fig. 1 b, the utility model embodiment circuit can reach precise dose compensation effect more through optimum Design of Parameters.

(7), above-mentioned (6) float the example that compensates to the temperature of the Vbe of T1, though be that variations in temperature through single temperature-sensing element (device) Rt realizes, also can be through electric current I 0 or divider resistance R1, R2 to variation of temperature; Perhaps adopt a plurality of temperature sensing element RTD to realize the temperature-compensating of multi-parameter.---such as, suppose that Rt is conventional, electric-resistance (not with variations in temperature), similar with the discussion of front formula 1, then, just can let them that Influence of Temperature is cancelled out each other according to the temperature variant characteristic △ I0 of following formula design adjustable parameter constant-current source I0:

△ I0=△ Vbe/Rt (formula 2)

Again such as; Adopt temperature sensing element RTD to substitute R2; Change Vs=Vout*R2/ (R1+R2) through the change divider resistance and carry out temperature-compensating, suppose that it is △ R2 that temperature is floated the R2 resistance change that causes, keep output voltage V out constant; The variable quantity of then exporting dividing potential drop sampled voltage Vs is △ Vs=Vout* △ R2*R1/ (R1+R2); Floating the Vbe junction voltage variable quantity that causes because of temperature when supposing the T2 balance again is △ Vbe, and then the variable quantity of dividing potential drop sampling resistor R2 calculates according to following formula, just can let them that Influence of Temperature is cancelled out each other:

△ R2=(1+R2/R1) * △ Vbe/Vout (formula 3)

(8), the example that compensates is floated to the temperature of T1 pipe Vbe in above-mentioned (6) and (7); Just how explanation adopts incorporate overall height temperature transistor arrangement to add the design philosophy of RTD (temperature-sensing element (device)) for ease, and its intention obviously is not limited only to adopt certain temperature sensitive device or certain fixing functional form.

Wherein, the adjustable parameter constant-current source can adopt adjustable resistance R0 to regulate electric current I 0.

Shown in Fig. 3 a, among the embodiment, the adjustable parameter constant-current source can be realized low power dissipation design based on the structure of JFET, specifically can comprise:

PN junction type fet JFET and adjustable resistance R0; Wherein:

Shown in Fig. 3 b, among the embodiment, the adjustable parameter constant-current source can be realized high-power driving based on transistorized structure, specifically can comprise:

Fig. 4 a to Fig. 4 d is several kinds of concrete structure signals of temperature-compensating and control circuit.Among the embodiment, temperature-compensating and control circuit can comprise: the serial or parallel connection circuit that adjustable RTD (Pt1000), fixed resistance (R0), thermistor (Rt), thermal diode (D) one of them or combination in any form.

Promptly; Regulate the R0 of I0 in the adjustable parameter constant-current source of Fig. 3 a, Fig. 3 b; Regulate the thermistor Rt of Vref in temperature-compensating and the control circuit; All can adopt elements such as Pt1000, thermistor Rt, thermal diode D or fixed resistance R, perhaps the structures such as series and parallel of these elements realize, referring to Fig. 4 a to Fig. 4 d.In addition; The RTD temperature-sensitive element both can be that positive temperature coefficient (PTC) also can be a negative temperature (NTC); Or the mode that is in parallel of the RTD that adopts positive temperature coefficient (PTC) and negative temperature (NTC); With the The optimal compensation effect that realizes that equality of temperature is not floated direction and different orders, referring to Fig. 5 a-1-Fig. 5 e-2 and follow-up relevant discussion.

(9), the compensating parameter of above-mentioned (1)-(8) regulates and optimal way, both can use separately, also can be optimized and integrated application wherein one or more; These parameters both can be used for the compensation of single circuit module; Can also be used for adjusting a plurality of circuit modules of power circuit simultaneously; Comprise composition modules such as adjustable parameter constant-current source, filter circuit, output voltage sampling circuit, feedback amplifier, voltage-regulating circuit and temperature-compensating and control circuit, to realize different temperatures scope, different compensation rate of change, the mode of approaching of different multinomial orders and the fine compensation of different output amplitude scopes.

About how utilizing more parameter to realize that equality of temperature not floats the linearity or the non-linear temperature compensation of direction, different orders; Particularly the downward best parabola compensation of quadratic function split shed specifies combination Fig. 5 a-1-Fig. 5 e-2 in follow-up effect, embodiment.

In a word; Through the use of temperature-sensing element (device) and the suitable selection of parameter; The power circuit of the utility model embodiment still all can form the negative feedback adjustment to the drift of temperature to the fluctuation of output voltage, thereby can reach the effect of auto thermal compensation and automatic voltage regulation simultaneously.Its major advantage is:

Adopt incorporate overall height temperature transistor arrangement to add the design that temperature-sensing element (device) (RTD) is done temperature-compensating, realize high temperature resistant, high voltage withstanding and high-power easily;

Adopt the variable element constant-current source to come while drive feedback amplifying circuit, voltage-regulating circuit and temperature-compensation circuit, only need suitably design constant current parameter, just can satisfy big input voltage range, wide temperature compensation range and good output stability simultaneously;

Adjustable parameter constant-current source and temperature-sensing element (device) (RTD) combine as the input of temperature-compensating, and parameter regulation has good independence and flexibility, can realize the accurate correction of various different temperature coefficients easily.

Many-sided comprehensive contrasts such as the flexibility of selecting from structural design and modularization debugging, the temperature compensation parameter of the utility model embodiment power circuit below, voltage stabilizing result of the test, the practical application effect of discussion the utility model embodiment.

1, circuit structure design more flexibly, be well suited for modular design debug pattern.

Discussion by Fig. 2 a and Fig. 2 b and front is not difficult to find out, each circuit module of the utility model embodiment is mainly divided according to function, and is simple in structure, interface is clear, and parameter regulation has good independence, is easy to modularized design and optimization; Device is selected also very flexible, need not as traditional temperature-compensation circuit, requires the device of pairing mutually that the consistent temperature characteristic is arranged.Such as; Regulate the R0 of I0 in the adjustable parameter constant-current source of Fig. 3 a, Fig. 3 b; Regulate the thermistor Rt of Vref in temperature-compensating and the control circuit; All can adopt elements such as Pt1000, thermistor Rt, thermal diode D or fixed resistance R, perhaps the structures such as series and parallel of these elements realize, referring to Fig. 4 a to Fig. 4 d.Therefore be easy to require (such as indexs such as withstand voltage, input range, pressure reduction requirement, power output, temperature range, power consumptions) to different input and output; Earlier each unit is carried out independent design and debugging; And then be integrated together the last unified again optimization of doing overall performance.This modular design debug pattern is very suitable for the batch process and the detection of streamline.

2, be easy to realize needed compensated curve, temperature-compensating is more accurate.

No matter selection changes I0, Rt still feeds back divider resistance R2 and realizes temperature-compensating, and its precision depends on all whether the parameter curve of compensating circuit can mate the temperature coefficient of element to be compensated fully.Because the RTD temperature-sensitive element both can be that positive temperature coefficient (PTC) also can be a negative temperature (NTC); And the RTD that adopts positive temperature coefficient (PTC) and negative temperature (NTC) plain mode of series and parallel mutually, just can realize from the temperature compensation curve of linearity, almost, quadratic function and higher order; Therefore, than adopting PN junction or diode to do the conventional method of temperature-compensating, the parameter regulation mode of the utility model embodiment has more flexibility, realizes the accurate correction of various different temperature coefficients more easily, and the temperature stability of circuit is better.

To combine Fig. 5 a-1-Fig. 5 e-2 to do below goes through.

Fig. 5 a-1 and Fig. 5 a-2 adopt linear temperature senser such as Pt RTD to realize the example (first compensation phase) of linear compensation, and wherein Fig. 5 a-1 is the examples of circuits figure that linear temperature senser realization linear compensation such as Pt RTD is adopted in temperature-compensating among the utility model embodiment with control circuit; Fig. 5 a-2 is the circuit temperature characteristic exemplary plot that linear temperature senser such as temperature-compensating and control circuit employing Pt RTD is realized linear compensations among the utility model embodiment; Its temperature characterisitic is following:

R (t)=R0+A*t (formula 4)

Fig. 5 b-1 and Fig. 5 b-2 are example (the approximate first compensation phases that limits the almost compensation of slope variation and maximum compensation range; Such as the linearisation of adopting R0 to NTC thermistor Rt), wherein Fig. 5 b-1 is that temperature-compensating and control circuit limit the examples of circuits figure that the almost of slope variation and maximum compensation range compensates among the utility model embodiment; Fig. 5 b-2 is the circuit temperature characteristic exemplary plot that temperature-compensating and control circuit limit the almost compensation of slope variation and maximum compensation range among the utility model embodiment; Its temperature characterisitic is following:

R (t) = \frac{R_{0} R_{C} + {AR}_{0} t}{(R_{0} + R_{C}) + At}

(formula 5)

Fig. 5 c-1 and Fig. 5 c-2 limit the example of standard 2 rank compensation of amplitude of variation and maximum compensation range (molecule are a parabolic equation; Denominator is a linear equation; When A1 and A2 near the time denominator be approximately constant), wherein Fig. 5 c-1 is the examples of circuits figure that temperature-compensating and control circuit limit the standard 2 rank compensation of amplitude of variation and maximum compensation range among the utility model embodiment; Fig. 5 c-2 is the circuit temperature characteristic exemplary plot that temperature-compensating and control circuit limit the standard 2 rank compensation of amplitude of variation and maximum compensation range among the utility model embodiment; Its temperature characterisitic is following:

R (t) = \frac{R_{1} R_{2} + (A_{1} R_{2} - A_{2} R_{1}) t - A_{1} A_{2} t^{2}}{(R_{1} + R_{2}) + (A_{1} - A_{2}) t}

(formula 6)

Fig. 5 d-1 and Fig. 5 d-2 are the special cases of Fig. 5 c-1 and Fig. 5 c-2; A1=A2=A; Also be the example (parabola compensation) that limits the 2 rank compensation of amplitude of variation and maximum compensation range, wherein Fig. 5 d-1 is that temperature-compensating and control circuit limit the examples of circuits figure that 2 rank of amplitude of variation and maximum compensation range compensate among the utility model embodiment; Fig. 5 d-2 is the circuit temperature characteristic exemplary plot that temperature-compensating and control circuit limit the 2 rank compensation of amplitude of variation and maximum compensation range among the utility model embodiment; Its temperature characterisitic is following:

R (t) = \frac{R_{1} R_{2} + A (R_{2} - R_{1}) t - A^{2} t^{2}}{R_{1} + R_{2}}

(formula 7)

Above-mentioned two kind of 2 rank compensated curve can reach the most smooth compensation effect (best second order compensation) at tp place, parabolical summit.Suppose that R1+R2=R0 remains unchanged, then the apex coordinate of Fig. 5 d-2 is:

\{\begin{matrix} t_{P} = \frac{R_{2} - R_{1}}{2 A} \\ R_{P} = {(\frac{R_{2} + R_{1}}{2})}^{2} = {(\frac{R_{0}}{2})}^{2} \end{matrix}

(formula 8)

The implementation of its circuit is:

The temperature coefficient of the positive temperature coefficient (PTC) of parallel connection and the RTD of negative temperature (NTC) keeps the equal and opposite in direction opposite in sign; Take to be with centre tapped potentiometer two ends to insert RTD respectively; And be connected to output from its tap of center of potentiometer; Just can realize regulating (R2 – R1) under the situation that R0=R1+R2 remains unchanged; To the second compensation function is that parabolical apex coordinate, opening direction, openings of sizes carry out independent control, thereby realizes the independent regulation and the optimization of (scope) and rate of change between The optimal compensation temperature spot (being that penalty function is the most steady in certain temperature spot tp place maintenance), maximum compensating basin.

This shows,, just can keep R as long as change temperature coefficient A _P=(R ₀/ 2) ²Change parabolical A/F and corresponding temperature t p=(the R2-R1)/2A in summit under the constant situation, thereby regulate the scope and the rate of change of compensation.

Another kind of mode is that parabolical A/F (that is: the rate of change of compensated curve) does not change, and does not just change temperature coefficient A, and the centre cap of a regulator potentiometer changes (R2-R1), thereby regulates the most steadily corresponding compensation temperature point tp in place.

Fig. 5 e-1 and Fig. 5 e-2 adopt the more example of the thermistor of high-order, and wherein Fig. 5 e-1 is that temperature-compensating and control circuit adopt the more examples of circuits figure of the thermistor of high-order among the utility model embodiment; Fig. 5 e-2 is that temperature-compensating and control circuit adopt the more circuit temperature characteristic exemplary plot of the thermistor of high-order among the utility model embodiment; Common PTC or NTC thermistor, if do not carry out the quasi-linearization compensation, its temperature characterisitic generally is that index changes, such as:

PTC thermistor: R (t)=R ₀(1-e ^-At) (formula 9)

NTC thermistor: R (t)=R ₀e ^-At(formula 10)

This shows; The mode that adopts positive temperature coefficient (PTC) and negative temperature (NTC) RTD to be in parallel; Add adjustable resistance or be with centre tapped potentiometer, be easy to realize different parameters and different multinomial orders---from the more effectively match of linearity, almost, quadratic function parabola that particularly Open Side Down and exponential function or the like compensated curve.In addition; The selection mode of above-mentioned penalty function; Both can use separately, also can carry out integrated application, to realize different temperatures scope, different compensation rate of change, the mode of approaching of different multinomial orders and the fine compensation of different output amplitude scopes wherein one or more.

Voltage-regulating circuit can also have multiple way of realization except that the structure shown in Fig. 2 b.For example, Fig. 6 a adopts NPN pipe T1 to setover over the ground to drive PNP pipe T3 and makes voltage-regulating circuit, can realize the structure of low pressure differential and low output voltage; Fig. 6 b adopts NPN pipe T1 that output is setovered and drives PNP (or IGBT) pipe T3 and make voltage-regulating circuit, can realize the structure of low-power consumption and low output voltage; Wherein export the divider resistance R1 of sampling, the further compensation of thermistor do that Rt2 (being the biasing resistor of T2) also can adopt PTC or NTC, with the precision and the temperature accommodation of raising power supply.

Concrete, voltage-regulating circuit shown in Fig. 6 a can comprise triode T1, T3 and fixed resistance R4;

The second end ground connection of fixed resistance R4.

Voltage-regulating circuit can comprise triode T1, T3 shown in Fig. 6 b;

Provide several instantiations below, the enforcement of power circuit among the utility model embodiment is described.

Embodiment one

In the present embodiment, the structure of power circuit is shown in Fig. 2 b, and wherein RTD adopts Pt1000 (zero degree resistance 1k ohm), and the adjustable parameter constant-current source adopts two kinds of structures of Fig. 3 a, Fig. 3 b respectively, and adopts variable resistor R0 to regulate electric current I 0.Fig. 3 a is the structure based on JFET because the reverse saturation conduction electric current I 0=Idss of JFET is smaller, generally at tens uA to several mA, under the bigger situation of the multiplication factor of adjustment pipe T1 (such as adopting Darlington transistor), can realize low power dissipation design; Fig. 3 b is based on transistorized structure, and electric current I 0 is regulated by resistance R 0, and scope can directly realize the driving of high-power pipe T1 more than tens uA to tens mA.JFET also can adopt the VMOS pipe to substitute and reach same low-power consumption and high-power driving effect; But because VMOS pipe maximum operating temperature is between 150 ℃ ~ 175 ℃; And the working temperature of high temperature crystal pipe and JFET all can reach-55 ℃ ~+200 ℃ scopes, so the selection of components and parts can be selected according to concrete needs flexibly.

The power circuit of present embodiment is produced testing and measuring technology and can be comprised the steps:

1, regulates dividing potential drop sampling resistor R1 and R2 earlier, output is stable near the output valve Vout that is designed; Regulate the R0 of adjustable parameter constant-current source again, make T1, T2 work in magnifying state.

2, improve ambient temperature (such as adopting the environmental impact test chamber), watch temperature and float wave characteristic,, increase I0 and Vref, make to export to reach temperature to float stability best the Temperature Compensation amplitude again according to fluctuation direction and size adjustment R0.Such as, floating the junction voltage Vbe variable quantity that causes because of temperature when supposing the T2 balance is △ Vbe, supposes that again it is △ Rt that temperature is floated the Rt resistance change that causes, then adjusts constant-current source through formula 1 previously discussed and just can let them that Influence of Temperature is offset fully:

I0=△Vbe/△Rt

3, above-mentioned repeatedly 1,2 liang of step, be transferred to the Vout that needs and reach best effect temperature compensation up to output.

4, can't be satisfied with if above-mentioned 1,2,3 steps are whole; △ Vbe can be decomposed into the stack of three parts; Be △ Vbe=△ Vbe0+ △ Vbe1+ △ Vbe2; Adopt temperature-sensing element (device) RTD to substitute the R0 of adjustable parameter constant-current source and the R2 in the bleeder circuit simultaneously, and according to formula 1 ~ formula 3 previously discussed, it is following to unite the corresponding temperature compensation parameter of adjustment:

I0=△ Vbe0/ △ Rt (formula 11)

△ I0=△ Vbe1/Rt (formula 12)

△ R2=(1+R2/R1) * △ Vbe2/Vout (formula 13)

Embodiment two

In the present embodiment, the structure of power circuit is shown in Fig. 6 a, and embodiment two with the difference of embodiment one mainly is:

Adopt NPN pipe T1 to setover over the ground to drive PNP pipe T3 and make voltage-regulating circuit, realizing the structure of low pressure differential (in the 1.0V) and low output voltage (about 2.4V), and reduce the shunting action of the base current I1 of T1 greatly constant-current source I0;

Wherein the temperature-compensating Rt1 to Vref adopts the littler Pt100 (100 ohm of zero degree resistance) of resistance;

If power consumption is too big, perhaps the temperature compensation range of Rt is not enough, then exports the divider resistance R1 of sampling, the further compensation of thermistor do that R2 (being the biasing resistor Rt2 of T2) also adopts PTC or NTC simultaneously, with the precision and the temperature accommodation of raising power supply.

It is identical with embodiment one that the power circuit of embodiment two is produced testing and measuring technology.

Embodiment three

In the present embodiment, the structure of power circuit can be thought the structure that adopts Darlington transistor corresponding to the T1 of Fig. 2 b shown in Fig. 6 b, and embodiment three with the difference of embodiment one mainly is:

Fig. 6 b adopts NPN pipe T1 that the output biasing is connected with PNP (or IGBT) pipe T3 and makes voltage-regulating circuit; With the structure of realization low-power consumption (power consumption depends primarily on the I0 of adjustable parameter constant-current source) and low output voltage, and reduce the shunting action of the base current I1 of T1 greatly to constant-current source I0;

Wherein the temperature-compensating Rt1 to Vref adopts the bigger Pt1000 (zero degree resistance 1k ohm) of resistance;

The divider resistance R1 of output sampling, the thermistor that R2 (being the biasing resistor of T2) also adopts PTC or NTC are simultaneously done further compensation, to improve the precision and the temperature accommodation of power supply.

The difference of embodiment three and instance two is that the emitter junction connected mode of NPN pipe T1 is different: embodiment two setovers over the ground, and three pairs of output biasings of embodiment.

It is identical with embodiment two that the power circuit of embodiment three is produced testing and measuring technology.

The power circuit result of the test of the power circuit that following comparative descriptions is traditional and the utility model embodiment.

Fig. 7 a is the traditional circuit of comparison of experimentizing, and corresponding to the structure of Fig. 1 a, Fig. 7 b is a practical implementation instance of the utility model, adopts the structure of Darlington transistor corresponding to the T1 of Fig. 2 b, or corresponding to the structure of Fig. 6 b.

Adopt Fig. 1 a and Fig. 6 b circuit structure to do test relatively, the design output voltage is+3.3V (normal temperature 25C, output loading Iout=15mA) that concrete circuit parameter is referring to Fig. 7 a and Fig. 7 b.Below table 1 to table 3 be respectively the output adjustment result comparisons of two kinds of circuit under identical Condition of Environment Changes, wherein Vout1 is corresponding to Fig. 7 a, Vout2 is corresponding to Fig. 7 b.Can see; The circuit construction of electric power of Fig. 7 b or the pairing the utility model embodiment of Fig. 6 b; To the adjustment better effects if of input voltage variation, output current (load) variation, variations in temperature, particularly temperature characterisitic and input fluctuation had good compensation and stablizing effect respectively.

Table 1: the output adjustment result (normal temperature 25C, output loading Iout=15mA) when input voltage vin changes

Input Vin (V)	5.0	10.0	15.0	20.0	25.0	30.0	35.0
								Output Vout1 (V)	3.08	3.21	3.30	3.39	3.46	3.54	3.61
Output Vout2 (V)	3.25	3.28	3.30	3.32	3.35	3.36	3.37

When Vin when 5.0V ~ 35V changes, Vout1=3.08V ~ 3.61V, amplitude of variation is 0.53V; And Vout2=3.25V ~ 3.37V, amplitude of variation has only 0.12V; Explain that adopting the variable element constant-current source to do the biasing excitation has good anti-incoming wave kinetic force.

Output adjustment result (normal temperature 25C, input voltage 15V) when table 2: output current Iout (load) changes

Output Iout (mA)	5.0	10.0	15.0	20.0	25.0	30.0	35.0
								Output Vout1 (V)	3.38	3.35	3.30	3.28	3.25	3.21	3.10
Output Vout2 (V)	3.33	3.32	3.30	3.29	3.27	3.25	3.24

[0172] When Iout when 5.0mA ~ 35.0mA changes, Vout1=3.38V ~ 3.10V, amplitude of variation is 0.28V; And Vout2=3.33V ~ 3.24V, amplitude of variation has only 0.09V.Explain that adopting the adjustable parameter constant-current source to do the biasing excitation has better anti-fluctuation of load ability.

Table 3: temperature is floated characteristic relatively (input voltage vin=15V, output load current Iout=15mA)

Temperature T (C)	0.0	25.0	50.0	75.0	100.0	125.0	150.0	175.0
									Output Vout1 (V)	3.39	3.30	3.26	3.20	3.13	2.91	2.62	1.80
Output Vout2 (V)	3.34	3.30	3.29	3.27	3.24	3.22	3.18	3.13

When temperature T when 0 ℃ ~ 175 ℃ change, Vout1=3.39V ~ 1.80V, amplitude of variation is 1.59V (when test finds that temperature 150C is above, 2.4V voltage-stabiliser tube and the rapid variation of high-temperature behavior that compensates diode among Fig. 7 a); And Vout2=3.34V ~ 3.13V, amplitude of variation has only 0.21V.Explain that the utility model embodiment has better temperature-compensating performance and hot operation ability.

In sum, the power circuit of the utility model embodiment still all can form the negative feedback adjustment to the drift of temperature to the fluctuation of output voltage, thereby can reach the effect of auto thermal compensation and automatic voltage regulation simultaneously.It adopts incorporate overall height temperature transistor arrangement to add the design that temperature-sensing element (device) (RTD) is done temperature-compensating, realizes high temperature resistant, high voltage withstanding and high-power easily; Adopt the variable element constant-current source to come while drive feedback amplifying circuit, voltage-regulating circuit and temperature-compensation circuit, only need suitably design constant current parameter, just can satisfy big input voltage range, wide temperature compensation range and good output stability simultaneously; Adjustable parameter constant-current source and temperature-sensing element (device) (RTD) combine as the input of temperature-compensating, and parameter regulation has good independence and flexibility, can realize the accurate correction of various different temperature coefficients easily.

The circuit construction of electric power of the utility model embodiment is simple, interface is clear, is easy to modularized design and optimization, and it is very flexible that each of power circuit formed the module device selection, but independent design and debugging, and then be integrated together; Therefore be easy to require (such as withstand voltage, input range, pressure reduction requirement, temperature range, power output etc.) to do design optimization to different input and output.

The power circuit of the utility model embodiment can be applicable to the oil reservoir logging field; Adapt to the down-hole high temperature stabilized voltage power supply design of wide input range, be particularly suitable for big under the hot environment to the input voltage fluctuation scope, power output is high, good stability, the low application scenario of temperature drift.Can also be applied to widely and in the electronic circuit input fluctuation senser big, that temperature drift is big carried out voltage and temperature-compensating.

Above-described specific embodiment; Purpose, technical scheme and beneficial effect to the utility model have carried out further explain, it should be understood that the above is merely the specific embodiment of the utility model; And be not used in the protection range that limits the utility model; All within the spirit and principle of the utility model, any modification of being made, be equal to replacement, improvement etc., all should be included within the protection range of the utility model.

Claims

1. a power circuit is characterized in that, comprising:

2. power circuit as claimed in claim 1 is characterized in that, the adjustable parameter constant-current source comprises:

PN junction type fet JFET and adjustable resistance R0; Wherein:

3. power circuit as claimed in claim 1 is characterized in that, the adjustable parameter constant-current source comprises:

4. power circuit as claimed in claim 1 is characterized in that voltage-regulating circuit comprises triode T1; Triode T1 is the NPN pipe; The current collection of triode T1 is first end of voltage-regulating circuit very; The emission of triode T1 is second end of voltage-regulating circuit very; The base stage of triode T1 is the control end of voltage-regulating circuit.

5. power circuit as claimed in claim 1 is characterized in that, voltage-regulating circuit comprises triode T1, T3 and fixed resistance R4;

The second end ground connection of fixed resistance R4.

6. power circuit as claimed in claim 1 is characterized in that voltage-regulating circuit comprises triode T1, T3;

7. power circuit as claimed in claim 1 is characterized in that feedback amplifier comprises triode T2; Triode T2 is the NPN pipe; The current collection of triode T2 is first end of feedback amplifier very; The emission of triode T2 is second end of feedback amplifier very; The base stage of triode T2 is the control end of feedback amplifier.

8. power circuit as claimed in claim 1 is characterized in that, temperature-compensating and control circuit comprise: the serial or parallel connection circuit that adjustable RTD, fixed resistance, thermistor, thermal diode one of them or combination in any form.

9. power circuit as claimed in claim 1 is characterized in that output voltage sampling circuit comprises: fixed resistance R1, adjustable resistance R2; First end of fixed resistance R1 is first end of output voltage sampling circuit; Second end of fixed resistance R1 links to each other with first end of adjustable resistance R2, and second end of fixed resistance R1 and first end of adjustable resistance R2 are second end of output voltage sampling circuit; Second end of adjustable resistance R2 is the 3rd end of output voltage sampling circuit.

10. power circuit as claimed in claim 1 is characterized in that filter circuit comprises capacitor C 1; First end of capacitor C 1 is first end of filter circuit; Second end of capacitor C 1 is second end of filter circuit.