CN102339081A

CN102339081A - High-precision numerical control saw-tooth constant current source

Info

Publication number: CN102339081A
Application number: CN2010102311204A
Authority: CN
Inventors: 张永炬; 王韬; 周强
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-07-15
Filing date: 2010-07-15
Publication date: 2012-02-01

Abstract

The invention relates to a high-precision numerical control saw-tooth constant current source and belongs to the field of electrician electronic products. The high-precision numerical control saw-tooth constant current source comprises a V/I (voltage/current) converting circuit, a pre-amplification circuit, a feedback circuit and a single chip system. In the saw-tooth constant current source, the V/I converting circuit is used for realizing output of a current; a single chip is used for controlling a D/A (digital/analog) outputted voltage so as to realize control of the current; the pre-amplification circuit is used for adjusting the D/A outputted voltage so as to cause the D/A outputted voltage to meet the demand on a voltage required by V/I conversion; the feedback circuit is used for feeding back outputted current information to the single chip, so as to realize closed-loop control; and an A/D module and a D/A module are arranged in the adopted single chip, so that additional A/D and D/A circuits are not needed. The high-precision numerical control saw-tooth constant current source has the advantages of low cost, high precision, excellent stability, and the like.

Description

A kind of high precision numerical control sawtooth constant current source

Technical field

The present invention relates to a kind of numerical control sawtooth constant-current source circuit, particularly relate to a kind of high precision numerical control sawtooth constant current source, belong to the electric and electronic product field.

Background technology

Along with the fast development of electronic technology, increasing industry all needs them to improve or test the performance index of Related product.Some fields need provide zigzag constant current source therein, perhaps as control signal or as test signal, realizing certain function or to test certain effect, and often need the correlation parameter of saw-tooth current be adjustable, can set.Because digital control scheme can provide control more accurately; So increasing product all develops toward the numerical control direction, also set at this correlation parameter of also hoping the sawtooth constant current source through digital control scheme, and traditional sawtooth constant current source often parameter can not set; So its function is very single; Can only be used for certain specific occasion, perhaps adopt the analog form precision not high, can't satisfy the related application demand.

Summary of the invention

The object of the present invention is to provide a kind of high precision numerical control sawtooth constant current source, make the sawtooth constant current source have more versatility, for related science research and product test provide comparatively practical platform.

The present invention realizes that the technical scheme that above-mentioned purpose is taked is: a kind of high precision numerical control sawtooth constant current source, and it is made up of V/I change-over circuit, pre-amplification circuit, feedback circuit and SCM system; Described V/I change-over circuit comprises integrated operational amplifier A2, triode Q1, Q2, adjustable resistance RW4, resistance R 13, R14, R15, R16, R17, Rp1, capacitor C 7, C8, C9, C10; They carry out the V/I conversion to realize constant current output to the voltage of D/A output; Triode Q1 and Q2 form Darlington transistor the electric current that V/I is converted to are amplified; To satisfy the requirement of big electric current output, RP1 is a sample resistance, as the feedback input of A2; Described pre-amplification circuit comprises integrated operational amplifier A1, adjustable resistance RW2, RW3, resistance R 10, R11, R12, realizes the negative feedback of D/A output voltage is amplified, and makes its output voltage satisfy the required voltage request of V/I conversion; Described feedback circuit comprises integrated operational amplifier A3, adjustable resistance RW5, RW6, resistance R 18, R19, R20, capacitor C 11, C12; It is nursed one's health into suitable Voltage Feedback with the voltage on the sampling resistor and returns A/D; Thereby realize the closed-loop control of total system, guaranteed the degree of accuracy and the degree of stability of output current; Described SCM system comprises single-chip microcomputer U1, liquid crystal LCD1, crystal oscillator Y1, ten mouthfuls of socket J1, pushbutton switch S1, S2, S3, S4, S5, S6, S7, adjustable resistance RW1, resistance R 1, R2, R3, R4, R5, R6, R7, R8, R9, capacitor C 1, C2, C3, C4, C5, C6; Keyboard S2, S3, S4, S5, S6, S7 are used for the setting of correlation function and parameter; Liquid crystal is used to show relevant information; The required voltage of D/A module output V/I conversion that single-chip microcomputer is built-in, the built-in A/D module of single-chip microcomputer realizes measurement and monitoring to output current.

Single-chip microcomputer U1 adopts C8051F020 type single-chip microcomputer in the said SCM system; The synchronizing pulse of system is through the 76 pin output of U1; The A/D conversion adopts the built-in A/D modules A DC0 of C8051F020 single-chip microcomputer to realize, outside voltage signal to be measured gets into ADC0 through the AIN0.0 pin; The D/A conversion adopts the built-in D/A module DAC0 of C8051F020 single-chip microcomputer to realize, and outwards exports D/A conversion voltage afterwards through the DAC0 pin; Display device adopts LCD1602 type liquid crystal to realize; The add-subtract control that setting, the S3 that keyboard S2 is used for the rise time is used for that sawtooth is set off time, S4 is used to be provided with single or cycle output, S5 is used to be provided with maximum output current, S6,7 is used for correlation parameter.

Said pre-amplification circuit adopts integrated operational amplifier OP07 to realize the negative feedback amplification of voltage.The voltage of D/A output links to each other with a wherein pin on adjustable resistance RW2 both sides; The RW2 another side links to each other with ground; After linking to each other with resistance R 11, middle adjustable end is connected into 3 pin of U1 again; Resistance R 10 1 ends link to each other with ground, and the other end links to each other with pin of

resistance R

12 and 2 pin of A1, and the other end of R12 follows 6 pin of A1 continuous.

The integrated operational amplifier A2 that is told in the V/I change-over circuit adopts OP07, and triode Q1 adopts 9012, and Q2 adopts TIP127 and it is installed on the large tracts of land heat radiator.Voltage is input to 2 pin of A2 through resistance R 13, and the two ends of R15 link to each other with emitter and the R17 of Q1 with 2 pin of A2 respectively, and another heel power supply of R17 is continuous; The base stage of Q1 links to each other with the emitter of Q2, and the collector of Q1 and the Q2 heel load RL that links to each other links to each other, and the base stage of Q2 is continuous with R16; The other end of R16 links to each other with 6 pin of A2, and the other end of load RL links to each other with employing resistance R p1 with R14, and the Rp1 other end links to each other with ground; The R14 other end links to each other with 3 pin of A2, and Q1, Q2 form current amplification circuit.

The C11 in C7 and C8, C9 and C10, the feedback circuit in the V/I change-over circuit of telling is connected in parallel separately with C13 and links to each other with ground with power supply respectively, and with realization filtering, wherein C7, C9, C12 select ceramic disc capacitor for use, and C8, C10, C11 adopt electrochemical capacitor.

The integrated operational amplifier A3 that is told in the feedback circuit adopts OP07.Voltage on the sample resistance Rp1 is through 3 pin of resistance R 18 inflow A3, and an end of resistance R 20 links to each other with 2 pin of A3 and the end of R19, and the other end of R19 links to each other with ground, and the other end of R20 is continuous with 6 pin of A3, thereby has formed negative feedback amplifier circuit jointly.The two ends of adjustable resistance RW6 link to each other with ground with 6 pin of A3 respectively, and the adjustable end in the middle of the RW5 links to each other with the AIN0.0 of single-chip microcomputer U1, and it realizes the voltage after amplifying is nursed one's health, and makes it satisfy the requirement of A/D conversion.

With control program, it also comprises casing in the described one-chip computer module, and display screen in the liquid crystal display circuit and keyboard are inlaid in respectively on the casing, and said each module all completes on a circuit board, and said circuit board is installed in the casing.

The invention has the beneficial effects as follows, the precision of sawtooth constant current source, stability are improved, greatly reduce cost, and adopt the mode use of numerical control to become more convenient.

Description of drawings

Fig. 1 is a system chart of the present invention.

Fig. 2 is the microcontroller system circuit schematic diagram.

Fig. 3 is the pre-amplification circuit schematic diagram.

Fig. 4 is a V/I change-over circuit schematic diagram.

Fig. 5 is the feedback circuit schematic diagram.

Fig. 6 is a saw-tooth current output synoptic diagram.

Embodiment

Below in conjunction with accompanying drawing the present invention is done further detailed description.

As shown in Figure 1, the present invention is a kind of high precision numerical control sawtooth constant current source, and it is made up of SCM system, pre-amplification circuit, V/I change-over circuit and feedback circuit.

Shown in Figure 2 is SCM system, and the parameter that it mainly realizes rise time, sawtooth off time and maximum output current is provided with and shows and function setting, D/A output, the A/D of single or the cycle sawtooth current output monitoring of sampling.Wherein U1 is a C8051F020 type single-chip microcomputer, and what S1, R2, R3, C3 and C4 formed is reset circuit, resets through pressing the S1 pushbutton switch when system moves when undesired; C5, C6 and Y1 form crystal oscillating circuit, and system clock is provided; J1, R1 are as the interface circuit of C8051F020 on-line debugging and download; S2, S3, S4, S5, S6, S7, R4, R5, R6, R7, R8, R9 form key circuit; When pressing button; With producing level translation from high to low on the continuous pin of single-chip microcomputer, detect button thus and whether press, and realize relative parameters setting and function setting; LCD1, RW1 form display circuit, show the constant current value of current setting, and LCD1 adopts LCD1602 type LCD, and RW1 is as the bright dark adjusting resistance of LCD backlight.

The built-in a plurality of A/D of C8051F020 type single-chip microcomputer, D/A module; Adopt ADC0 and DAC0 module respectively at this; Both reference voltages all adopt internal reference voltage, and single-chip microcomputer will send to DAC0 by the numerical value of key assignments and carry out the D/A conversion, and export correspondent voltage from the DAC0 pin of single-chip microcomputer.The current value range of this sawtooth constant current source output is that 20mA is to 2A; And the magnitude of voltage of DAC0 pin output can't satisfy 20mA to the required magnitude of voltage of 2A scope V/I conversion; So can't the DAC0 pin directly be linked to each other with the V/1 change-over circuit, the centre must add the one-level pre-amplification circuit and amplify, nurses one's health with the voltage to the output of DAC0 pin.R10, R11, R12, RW2, RW3, A1 have constituted the negative feedback type pre-amplification circuit jointly, and be as shown in Figure 3, and A1 adopts OP07 type integrated operational amplifier; R10, R12 confirm enlargement factor; RW2 constitutes a bleeder circuit, regulates input voltage range, thereby makes the voltage after the amplification satisfy the correlation parameter requirement; RW3 is a zero-regulator resistor, makes A1 guarantee that when zero input output also is zero.

Being admitted to A2, Q1, Q2 through the voltage after the preposition amplification conditioning is the V/I change-over circuit of core; As shown in Figure 4, this voltage is through 3 pin of resistance R 13 inflow A2, and 3 pin of A2 are returned in the output of A2 through resistance in series network R14, R16, RL positive feedback; Thereby 2 pin that return A2 through resistance in series network R15, R16 negative feedback are realized the V/I change-over circuit; The end of sample resistance RP1 links to each other with the end of R14, RL, and the other end links to each other with ground, and RL is a pull-up resistor.Because the current value that is converted to through V/I can't reach 2A; So added the current amplification circuit of forming by Q1, Q2 thereafter; Q1 adopts 9012 earlier electric current to be carried out elementary amplification, and Q2 adopts TIP127, and the base current of Q1 flows directly into the emitter-base bandgap grading of Q2; Thereby realize the amplification once more of electric current, to reach the requirement of 2A.Link to each other with the positive pole of 18V power supply and the collector of Q1, Q2 respectively at the two ends of this load, so Q1, the last collector current sum that flows through of Q2 are the current value in the load.Capacitor C 7, C8 and C9, C10 form filtering circuit separately, thereby increase the stability of system, and RW4 makes A2 guarantee that when zero input output also is zero as the zero-regulator resistor of A2.

We have realized constant current output in the preceding circuit; But whether the current value of output is exactly the value that we set, and whether precision reaches requirement, and perhaps circuit has and cannot the generation wild effect cause current value to depart from; These all can't be discerned; We have added feedback sense circuit at this in order to realize these, thereby make total system become a closed-loop system, increase the reliability and stability of system.Here we feed back the Vback voltage on the sample resistance to detect current current value; Single-chip microcomputer utilizes its built-in A/D modules A DC0 to realize the A/D conversion; Obtain the Vback magnitude of voltage; But the Vback magnitude of voltage does not match with the reference voltage value of ADC0, thus add that at this feedback circuit nurses one's health Vback voltage, as shown in Figure 5.Vback gets into 3 pin of A3 through resistance R 18; R20 couples together 2 pin and 6 pin of U3; R19 links to each other with ground with 2 pin of A2 respectively, and they have formed a negative feedback amplifier circuit jointly, passes to the AIN0.0 pin of single-chip microcomputer after the voltage dividing potential drop of adjustable resistance RW6 with U3 output.After the conditioning through feedback circuit, the magnitude of voltage of Vback will satisfy related request.

Through just realizing constant current output behind the above circuit; In order to realize required sawtooth current output, set correlation parameter as shown in Figure 6: the parameter setting of rise time ti, sawtooth tp off time and maximum output current Imax and function setting single or cycle sawtooth current output through S2, S3, S4, S5, S6, S7 button.If set rise time ti, at first press S2 and make system be in ti parameter setting state, and then, withdraw from by the S2 key more at last through pressing plus-minus that S6, S7 realize correlation to reach desired value; If set sawtooth tp off time, at first press S3 and make system be in tp parameter setting state, and then, withdraw from by the S3 key more at last through pressing plus-minus that S6, S7 realize correlation to reach desired value; If set maximum output current Imax, at first press S4 and make system be in Imax parameter setting state, and then, withdraw from by the S4 key more at last through pressing plus-minus that S6, S7 realize correlation to reach desired value; If set single or cycle sawtooth current output, at first press S5 and make system be in this function setting state, and then realize the switching of correlation behavior through pressing S6, S7, withdraw from by the S5 key more at last.After correlation parameter and function be set, system will go up the output saw-tooth current according to being set in RL, and exports a synchronizing pulse at 76 pin of U1.

Claims

1. high precision numerical control sawtooth constant current source, it is characterized in that: it is made up of V/I change-over circuit, pre-amplification circuit, feedback circuit and SCM system; Described V/I change-over circuit comprises integrated operational amplifier A2, triode Q1, Q2, adjustable resistance RW4, resistance R 13, R14, R15, R16, R17, Rp1, capacitor C 7, C8, C9, C10; They carry out the V/I conversion to realize constant current output to the voltage of D/A output; Triode Q1 and Q2 form Darlington transistor the electric current that V/I is converted to are amplified; To satisfy the requirement of big electric current output, RP1 is a sample resistance, as the feedback input of A2; Described pre-amplification circuit comprises integrated operational amplifier A1, adjustable resistance RW2, RW3, resistance R 10, R11, R12, realizes the negative feedback of D/A output voltage is amplified, and makes its output voltage satisfy the required voltage request of V/I conversion; Described feedback circuit comprises integrated operational amplifier A3, adjustable resistance RW5, RW6, resistance R 18, R19, R20, capacitor C 11, C12; It is nursed one's health into suitable Voltage Feedback with the voltage on the sampling resistor and returns A/D; Thereby realize the closed-loop control of total system, guaranteed the degree of accuracy and the degree of stability of output current; Described SCM system comprises single-chip microcomputer U1, liquid crystal LCD1, crystal oscillator Y1, ten mouthfuls of socket J1, pushbutton switch S1, S2, S3, S4, S5, S6, S7, adjustable resistance RW1, resistance R 1, R2, R3, R4, R5, R6, R7, R8, R9, capacitor C 1, C2, C3, C4, C5, C6; Keyboard S2, S3, S4, S5, S6, S7 are used for the setting of correlation function and parameter; Liquid crystal is used to show relevant information; The required voltage of D/A module output V/I conversion that single-chip microcomputer is built-in, the built-in A/D module of single-chip microcomputer realizes measurement and monitoring to output current.

2. a kind of high precision numerical control sawtooth constant current source according to claim 1 is characterized in that: single-chip microcomputer U1 adopts C8051F020 type single-chip microcomputer in the said SCM system; The synchronizing pulse of system is through the 76 pin output of U1; The A/D conversion adopts the built-in A/D modules A DC0 of C8051F020 single-chip microcomputer to realize, outside voltage signal to be measured gets into ADC0 through the AIN0.0 pin; The D/A conversion adopts the built-in D/A module DAC0 of C8051F020 single-chip microcomputer to realize, and outwards exports D/A conversion voltage afterwards through the DAC0 pin; Display device adopts LCD1602 type liquid crystal to realize; The add-subtract control that setting, the S3 that keyboard S2 is used for the rise time is used for that sawtooth is set off time, S4 is used to be provided with single or cycle output, S5 is used to be provided with maximum output current, S6,7 is used for correlation parameter.

3. a kind of high precision numerical control sawtooth constant current source according to claim 1 is characterized in that: said pre-amplification circuit adopts integrated operational amplifier OP07 to realize the negative feedback amplification of voltage.The voltage of D/A output links to each other with a wherein pin on adjustable resistance RW2 both sides; The RW2 another side links to each other with ground; After linking to each other with resistance R 11, middle adjustable end is connected into 3 pin of U1 again; Resistance R 10 1 ends link to each other with ground, and the other end links to each other with pin of resistance R 12 and 2 pin of A1, and the other end of R12 follows 6 pin of A1 continuous.

4. a kind of high precision numerical control sawtooth constant current source according to claim 1 is characterized in that: the integrated operational amplifier A2 that is told in the V/I change-over circuit adopts OP07, and triode Q1 adopts 9012, and Q2 adopts TIP127 and it is installed on the large tracts of land heat radiator.Voltage is input to 2 pin of A2 through resistance R 13, and the two ends of R15 link to each other with emitter and the R17 of Q1 with 2 pin of A2 respectively, and another heel power supply of R17 is continuous; The base stage of Q1 links to each other with the emitter of Q2, and the collector of Q1 and the Q2 heel load RL that links to each other links to each other, and the base stage of Q2 is continuous with R16; The other end of R16 links to each other with 6 pin of A2, and the other end of load RL links to each other with employing resistance R p1 with R14, and the Rp1 other end links to each other with ground; The R14 other end links to each other with 3 pin of A2, and Q1, Q2 form current amplification circuit.

5. a kind of high precision numerical control sawtooth constant current source according to claim 1; It is characterized in that: the C11 in C7 and C8, C9 and C10, the feedback circuit in the V/I change-over circuit of telling is connected in parallel separately with C13 and links to each other with ground with power supply respectively; To realize filtering; Wherein C7, C9, C12 select ceramic disc capacitor for use, and C8, C10, C11 adopt electrochemical capacitor.

6. a kind of high precision numerical control sawtooth constant current source according to claim 1 is characterized in that: the integrated operational amplifier A3 that is told in the feedback circuit adopts OP07.Voltage on the sample resistance Rp1 is through 3 pin of resistance R 18 inflow A3, and an end of resistance R 20 links to each other with 2 pin of A3 and the end of R19, and the other end of R19 links to each other with ground, and the other end of R20 is continuous with 6 pin of A3, thereby has formed negative feedback amplifier circuit jointly.The two ends of adjustable resistance RW6 link to each other with ground with 6 pin of A3 respectively, and the adjustable end in the middle of the RW5 links to each other with the AIN0.0 of single-chip microcomputer U1, and it realizes the voltage after amplifying is nursed one's health, and makes it satisfy the requirement of A/D conversion.

7. a kind of high precision numerical control sawtooth constant current source according to claim 2; It is characterized in that: in the described one-chip computer module with control program; It also comprises casing; Display screen in the liquid crystal display circuit and keyboard are inlaid in respectively on the casing, and said each module all completes on a circuit board, and said circuit board is installed in the casing.