CN112688161B - Driving current source of narrow-linewidth semiconductor laser for cold atom gyroscope - Google Patents
Driving current source of narrow-linewidth semiconductor laser for cold atom gyroscope Download PDFInfo
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Abstract
The invention relates to a driving current source of a narrow-linewidth semiconductor laser for a cold atom gyroscope, which comprises a power supply module, a negative feedback module and a scanning input module which are sequentially connected, wherein the power supply module comprises a first-stage linear voltage stabilizer and a second-stage linear voltage stabilizer which are connected in series, and the first-stage linear voltage stabilizer is used for inhibiting noise from a power supply and providing multiple paths of positive voltage and negative voltage after first-stage conversion; the second stage linear voltage regulator is used for further reducing the noise of the output current and providing the converted voltage of the second stage; the negative feedback module is used for sampling the output voltage of the second-stage linear voltage stabilizer, performing operation on the output voltage and a set reference voltage and then controlling to output a constant current signal, wherein the reference voltage is referred to the output of the second-stage linear voltage stabilizer; the scanning input module is connected with a load and is used for superposing a scanning current signal on the constant current signal so as to lock the frequency of the constant current signal. The invention has the advantages of low current noise, high direct current stability, high modulation speed and low cost.
Description
Technical Field
The invention relates to the technical field of cold atom interference, in particular to a driving current source of a narrow-linewidth semiconductor laser for a cold atom gyroscope.
Background
The inertial navigation is a navigation technology with complete autonomy and strong anti-interference capability, and the gyroscope is a core sensor of the inertial navigation system. The inertial navigation system formed by the existing fiber-optic gyroscope and laser gyroscope is limited by the long-term stability and the accumulation of errors, has a larger difference with the GPS satellite navigation system, and the novel atomic gyroscope has high precision and sensitivity and can make up the defects of the prior inertial navigation system. The atomic gyroscope is a high-performance sensor for sensing external rotation by utilizing an atomic spectrum, and has great development potential and application value in the fields of satellite attitude adjustment, terrain measurement and inertial navigation. In the working process of the cold atom beam gyroscope, the atoms need to be cooled, imprisoned and accurately controlled by laser with narrow line width and low phase noise, so that the measurement accuracy and sensitivity of the atom gyroscope are directly influenced by the line width of the laser. The semiconductor laser needs to be driven by a constant current source, and population inversion occurs when the number of carriers reaches a certain degree, which provides a necessary condition for laser generation. Since the noise and stability of the constant current source directly determine the output line width of the semiconductor laser, it is necessary to design a low-noise and high-stability constant current source as a driving current source for the narrow-line-width semiconductor laser.
Disclosure of Invention
The invention provides a driving current source of a narrow-linewidth semiconductor laser for a cold atom gyroscope, aiming at the technical problems in the prior art, and overcoming the defects of large ripple noise, low stability and the like of the driving current source of a common narrow-linewidth semiconductor laser.
The technical scheme for solving the technical problems is as follows:
a driving current source of a narrow-linewidth semiconductor laser for a cold atom gyroscope comprises a power supply module, a negative feedback module and a scanning input module which are sequentially connected, wherein the power supply module comprises a first-stage linear voltage stabilizer and a second-stage linear voltage stabilizer which are connected in series,
the input of the first-stage linear voltage stabilizer is connected with the power supply, and the output of the first-stage linear voltage stabilizer is connected with the negative feedback module and is used for suppressing noise from the power supply and providing multiple paths of positive voltage and negative voltage after first-stage conversion;
the input of the second-stage linear voltage stabilizer is connected with the positive voltage output end of the first-stage linear voltage stabilizer, and the output of the second-stage linear voltage stabilizer is connected with the negative feedback module and the scanning input module and is used for further reducing the noise of output current and providing voltage after second-stage conversion;
the negative feedback module is connected with the output of the second-stage linear voltage stabilizer and is used for sampling the output voltage of the second-stage linear voltage stabilizer, calculating the output voltage with a set reference voltage and controlling to output a constant current signal, wherein the reference voltage is referred to the output of the second-stage linear voltage stabilizer;
the scanning input module and the output of the negative feedback module are connected in parallel to a load and used for superposing a scanning current signal on the constant current signal so as to lock the frequency of the constant current signal.
Further, the negative feedback module comprises an operational amplifier, a reference source, a sampling resistor and a PMOS (P-channel metal oxide semiconductor) tube, wherein the source electrode of the PMOS tube is connected with the output of the second-stage linear voltage stabilizer, the drain electrode of the PMOS tube is connected with a load in series and then is grounded, and the grid electrode of the PMOS tube is connected with the output end of the operational amplifier; the sampling resistor is arranged between the output of the second-stage linear voltage stabilizer and the source electrode of the PMOS tube, and the sampling resistor is connected with the reverse input end of the operational amplifier; the same-direction input end of the operational amplifier is connected with the output end of the reference source, and the power supply input end of the operational amplifier is connected with the output of the first-stage linear voltage stabilizer; the positive pole of the reference source is connected with the output of the second-stage linear voltage stabilizer, the negative pole of the reference source is connected with the negative voltage output end of the first-stage linear voltage stabilizer, and the reference source is provided with reference voltage. The output of the second-stage linear voltage stabilizer is used as a reference voltage by the reference source, so that common-mode noise is suppressed; and the negative electrode of the reference source is not grounded, so that noise from the ground can be suppressed.
The reference source comprises a voltage-stabilizing tube and a potentiometer which are connected in parallel, the cathode of the voltage-stabilizing tube and the anode of the potentiometer are connected in parallel with the output of the second-stage linear voltage stabilizer, the anode of the voltage-stabilizing tube and the cathode of the potentiometer are connected in parallel and then connected with the negative voltage output end of the first-stage linear voltage stabilizer through a pull-down resistor, and the output end of the potentiometer is connected with the same-direction input end of the operational amplifier.
Further, a feedback coefficient conditioning circuit is arranged between the sampling resistor and the reverse input end of the operational amplifier.
Furthermore, the source electrode of the PMOS tube is also provided with an equal proportion monitoring circuit for monitoring the equal proportion voltage signal of the source electrode of the PMOS tube.
Further, a filter circuit is arranged on the drain electrode of the PMOS tube, and the filter circuit is arranged between the drain electrode of the PMOS tube and the scanning input module.
Furthermore, the first-stage linear voltage regulator comprises two parallel power supply conversion modules, wherein one power supply conversion module is used for converting a positive power supply input into a first-stage positive voltage output, and the other power supply conversion module is used for converting a negative power supply input into a first-stage negative voltage output.
Further, the second stage linear regulator is configured to convert the first stage positive voltage output to a second stage positive voltage output.
The protection circuit comprises a protection diode arranged in a forward bias mode, the anode of the protection diode is connected with the current input end of the load, the cathode of the protection diode is grounded, and the forward conduction voltage drop of the protection diode is higher than that of the load.
The invention has the beneficial effects that: the constant current source framework provided by the invention isolates the key control signal output by constant current from the noise potential surface, and filters most of noise in the circuit by applying a common mode denoising mode; and then, directly injecting a scanning current into a drain of the PMOS tube in a VI conversion mode of the operational amplifier, and locking the output frequency of the laser. The invention has the advantages of low current noise, extremely high direct current stability and high speed modulation capability, adopts the linear voltage stabilizer for voltage conversion and has low cost.
Drawings
FIG. 1 is a schematic diagram of a conventional constant current source for a laser;
FIG. 2 is a schematic diagram of a system configuration according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a power supply relationship of a power supply module according to an embodiment of the invention;
FIG. 4 is a schematic diagram of a reference source circuit according to an embodiment of the present invention;
FIG. 5 is a schematic circuit diagram of a scan input module according to an embodiment of the present invention;
FIG. 6 is a simplified circuit diagram of a scan input module according to an embodiment of the present invention;
FIG. 7 shows the results of the long-term stability test of the examples of the present invention.
Detailed Description
The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.
Fig. 1 shows a prior art laser constant current source, which is based on an NMOS transistor, and a laser load is directly connected to an output of a power supply, and a current flowing through the laser load is sampled by a sampling resistor and sent to an inverting input terminal of a feedback module. As can be seen from the characteristics of the NMOS transistor, when it is operated in the saturation region, the magnitude of the current flowing through the source is determined by the voltage V between the gate and the sourceGS. At this time: for an N-type MOS tube, the voltage relation of drain, grid and source tripoles is as follows:
VD＞VG＞VS (1)
the conditions to reach the constant flow zone are:
VGS＞Vth (2)
Vththe threshold voltage of the NMOS transistor is related to the material of the NMOS transistor, and the threshold voltage of the silicon material is generally about 0.7V.
When an N-type MOS transistor is used, the sampling resistor is connected between the source and GND, and the load is connected between the power supply and the drain, the following relationship can be obtained:
VS＝VGNDnoise+IS×RS (3)
as can be seen from the above equation (3), the source voltage V at this timeSReference via GND. Since most circuit designs have multiple components of noise coupled to GND, which is a reference plane with large noise relative to other potential planes, V in the designSThere will be a large noise. And a gate voltage VGIs dependent on the reference voltage VSETSince the GND plane does not have common mode noise with any plane, it is clear that V isGIs a differential mode noise which is difficult to filter out, but the final gate-source voltage V isGSThe noise of (2) is reflected in a superposition form of the two noises, and finally, the noise of the output current is also increased.
Fig. 2 is a schematic diagram of a system structure of a driving current source of a narrow-linewidth semiconductor laser for a cold atomic gyroscope according to this embodiment, which includes a power supply module, a negative feedback module, and a scan input module, which are connected in sequence, where the power supply module includes a first-stage linear regulator and a second-stage linear regulator connected in series,
the input of the first-stage linear voltage stabilizer is connected with the power supply, and the output of the first-stage linear voltage stabilizer is connected with the negative feedback module and is used for suppressing noise from the power supply and providing multiple paths of positive voltage and negative voltage after first-stage conversion;
the input of the second-stage linear voltage stabilizer is connected with the positive voltage output end of the first-stage linear voltage stabilizer, and the output of the second-stage linear voltage stabilizer is connected with the negative feedback module and the scanning input module and is used for further reducing the noise of output current and providing voltage after second-stage conversion;
the negative feedback module is connected with the output of the second-stage linear voltage stabilizer and is used for sampling the output voltage of the second-stage linear voltage stabilizer, calculating the output voltage with a set reference voltage and controlling to output a constant current signal, wherein the reference voltage is referred to the output of the second-stage linear voltage stabilizer;
the scanning input module and the output of the negative feedback module are connected in parallel to a load and used for superposing a scanning current signal on the constant current signal so as to lock the frequency of the constant current signal.
The output of the second-stage linear voltage stabilizer supplies power for the laser load, the reference voltage of the negative feedback module takes the output of the second-stage linear voltage stabilizer as reference, and common-mode noise is removed by adopting a common-mode noise removal mode.
Furthermore, the first-stage linear voltage regulator comprises two parallel power supply conversion modules, wherein one power supply conversion module is used for converting a positive power supply input into a first-stage positive voltage output, and the other power supply conversion module is used for converting a negative power supply input into a first-stage negative voltage output. The two power supply conversion modules are realized by adopting linear voltage stabilization chips, and have higher power supply rejection ratio, so that noise of most frequency bands can be suppressed. Fig. 3 is a schematic diagram of a power supply relationship of a power supply module, in which a chip LT1963 and a chip LT3015 belong to a first-stage linear regulator, which converts an input +15V power supply voltage into a +12V voltage (i.e., a first-stage positive voltage) and converts an input-15V power supply voltage into a-12V voltage (i.e., a first-stage negative voltage) for providing an operating power supply for an operational amplifier and a reference source in a negative feedback module mentioned later.
In this embodiment, the second stage linear regulator is a chip LT3045 shown in fig. 3, and is configured to convert the first stage positive voltage (+12V) output into a second stage positive voltage (+10V) output, where the second stage positive voltage (+10V) provides a working power supply for a laser load, and provides a reference for a reference voltage of a negative feedback module, so as to achieve a common mode noise reduction effect.
As shown in fig. 2, the negative feedback module includes an operational amplifier, a reference source, a sampling resistor, and a PMOS transistor, wherein a source of the PMOS transistor is connected to an output of the second stage linear regulator, a drain of the PMOS transistor is connected in series with a load and then grounded, and a gate of the PMOS transistor is connected to an output terminal of the operational amplifier; the sampling resistor is arranged between the output of the second-stage linear voltage stabilizer and the source electrode of the PMOS tube, and the sampling resistor is connected with the reverse input end of the operational amplifier; the same-direction input end of the operational amplifier is connected with the output end of the reference source, and the power supply input end of the operational amplifier is connected with the output (+/-12V) of the first-stage linear voltage stabilizer; the positive pole of the reference source is connected with the output (+10V) of the second-stage linear voltage stabilizer, the negative pole of the reference source is connected with the negative voltage output end (-12V) of the first-stage linear voltage stabilizer, and the reference source is provided with reference voltage. The reference source takes the output (+10V) of the second-stage linear voltage regulator as a reference voltage, and common-mode noise is suppressed; and the negative electrode of the reference source is not grounded, so that noise from the ground can be suppressed.
As shown in fig. 4, the reference source includes a voltage regulator tube and a potentiometer connected in parallel, a cathode of the voltage regulator tube and an anode of the potentiometer are connected in parallel to an output of the second-stage linear voltage regulator, an anode of the voltage regulator tube and a cathode of the potentiometer are connected in parallel and then connected to a negative voltage output terminal of the first-stage linear voltage regulator through a pull-down resistor, and an output terminal of the potentiometer is connected to a same-direction input terminal of the operational amplifier. In this embodiment, the function of the voltage regulator tube is realized by using a chip LM399, and the function of the potentiometer is realized by using a bernes potentiometer. The power supply end of the chip LM399 and the positive electrode of the potentiometer are connected in parallel with the output (+10V) of the second-stage linear voltage stabilizer, and the grounding pin of the chip LM399 is connected in parallel with the negative electrode of the potentiometer and then connected with the negative voltage output end (-12V) of the first-stage linear voltage stabilizer through a pull-down resistor. Since the negative electrode of the reference source is not grounded, noise from the ground can be suppressed.
Preferably, in this embodiment, a feedback coefficient conditioning circuit is disposed between the sampling resistor and the inverting input terminal of the operational amplifier.
Preferably, in this embodiment, the source of the PMOS transistor is further provided with an equal proportion monitoring circuit for monitoring an equal proportion voltage signal of the source of the PMOS transistor.
Preferably, in this embodiment, a filter circuit is disposed at the drain of the PMOS transistor, and the filter circuit is disposed between the drain of the PMOS transistor and the scan input module.
As a preferable scheme, in this embodiment, the constant current source of this embodiment further includes a protection circuit, the protection circuit includes a protection diode arranged in a forward bias manner, an anode of the protection diode is connected to the current input terminal of the load, a cathode of the protection diode is grounded, and a forward conduction voltage drop of the protection diode is higher than a forward conduction voltage drop of the load. Generally, the diode has a low conduction voltage drop, so that when the parameters of the protection diode are selected, the protection can be achieved only by making the conduction voltage drop of the protection diode slightly higher than that of the laser diode serving as a load. The selection of specific parameters needs to be determined according to the laser actually used, and is not described herein again. When the current is overlarge, the voltage at two ends of the load is increased, when the forward conduction voltage of the protection diode is reached, the protection diode is conducted, and the overlarge current flows to the ground through the protection diode, so that the effect of protecting the load laser is achieved.
The working principle is as follows:
fig. 3 is a diagram illustrating a relationship between the power supply module supplying power to the feedback module and the load. The positive power supply part of the constant current source adopts the design of a two-stage linear voltage regulator, and the linear voltage regulator (LDO) has extremely high power supply rejection ratio and common mode rejection ratio, so that most of noise from a power supply can be effectively suppressed by the design. The noise in the negative power supply in the whole circuit has small influence on the stability of the output current, so the negative power supply can meet the requirement only through one linear voltage stabilizer. The linear voltage stabilizer has the advantages of low output noise, low cost and the like.
The first stage linear regulator uses two linear regulator (LDO) chips, LT1963 and LT3015 shown in FIG. 3, to convert the +15V voltage of the input power source into +12V voltage output and the-15V voltage into-12V voltage output, respectively. Because the operational amplifier and the linear voltage regulator have higher power supply rejection ratio, most of noise in frequency bands can be suppressed, so that the second-stage power supply has stronger on-load capacity and lower output noise requirement. And a linear voltage regulator chip LT3045 is connected in series behind the +12V output voltage to serve as a second-stage linear voltage regulator, the +12V voltage is converted into +10V voltage to be output, and power is supplied to a laser load through a PMOS (P-channel metal oxide semiconductor) tube. The power supply of the part directly influences the output of the constant current source, so that higher requirements are placed on the power supply of the part, and the applicant uses a linear power supply LT3045 with low noise after the power supply of +12V to further reduce the noise of the output current.
The +/-12V voltage output by the first-stage linear voltage stabilizer provides a working power supply for an operational amplifier in the negative feedback module, and the +10V voltage output by the second-stage linear voltage stabilizer provides a reference voltage for a reference source in the negative feedback module, so that common-mode noise is removed; the negative pole of the reference source is connected with the-12V voltage output by the linear voltage stabilizer. The negative pole of the reference source avoids grounding, and effectively inhibits noise from the ground.
As shown in fig. 2, the negative feedback module samples the voltage of the source of the PMOS transistor through the sampling resistor, and after the voltage is processed by the feedback coefficient conditioning circuit, the voltage is introduced into the inverting input terminal of the operational amplifier to control the output of the operational amplifier, and then the output of the operational amplifier directly drives the gate voltage of the PMOS transistor to control the output current of the whole constant current source. The reference source adopts +10V output by the second-stage linear voltage stabilizer as reference voltage, and the reference voltage can be adjusted between 0V and 10V through a potentiometer of the reference source.
The whole negative feedback module feeds back the voltage of the sampling resistor to the reverse input end of the operational amplifier to control the output of the operational amplifier, and then the output of the operational amplifier directly drives the grid voltage of the PMOS tube, thereby controlling the output current of the whole constant current source. The negative feedback in the current constant current source is not negative feedback in the traditional sense, and the output end of the negative feedback is not directly connected and fed back to the reverse input end of the operational amplifier through the sampling resistor as shown in fig. 1, but drives the PMOS transistor through the output voltage as shown in fig. 2, and then generates a constant current signal, and the constant current signal is converted into a voltage signal through the sampling resistor and fed back to the reverse input end of the operational amplifier by utilizing the constant current characteristic of the PMOS transistor. The gain of input and output of the operational amplifier is difficult to analyze by adopting a common virtual short and virtual break method of a negative feedback circuit, and the output gain of the operational amplifier not only depends on the coefficient of a feedback resistor, but also depends on the constant current characteristic of an MOS (metal oxide semiconductor) tube. Different MOS transistors can correspond to different operational amplifier output gains, so that the operational amplifier is directly regarded as a method in open loop gain to analyze the circuit, and the specific analysis method is shown as follows.
The voltage input by the same-direction input end of the operational amplifier is set as VSETFeedback voltage of inverting input terminal is V-Output voltage of VOUTAnd the open-loop gain is k, and according to an open-loop gain formula of the operational amplifier:
VOUT＝k(VSET-V_) (4)
let the current flowing through the sampling resistor be ISThe sampling resistance is RSamplingAnd then:
V_＝IS×Rsampling (5)
The positive voltage of the operational amplifier is denoted as VCCThe voltage corresponds to the positive voltage +12V output by the first stage linear voltage regulator, and the negative voltage of the operational amplifier is marked as VDDThis voltage corresponds to the negative voltage-12V output by the first stage linear regulator. Suppose that V is adjusted wellSETSet it to be ratio VCCA value smaller than 1V, such that VCCThere was a mutation from 0 to 10V. When the current flowing through the sampling resistor is considered to be zero at the moment of power-on, V at that moment-＝VCC. Since the open loop gain k of the operational amplifier is a large value, generally calculated in dB, V is now the caseOUT＝VDDThen the grid voltage V of PMOS tubeG＝VDDSource voltage VS＝VCCThe two types can be converted into the grid source voltage V of the PMOS tubeGS＝VDD-VCC. At this time VGSWhen the absolute value of (A) is very large, the gate-source voltage V of the PMOS tubeGSA large negative value. Source current I of PMOS tubeSAnd gate source voltage VGSIs in positive correlation, the gate voltage V is thenGCorresponding to a state of a large current, in which a negative feedback is not established in a very short time, the source current ISWill be pulled up quickly. With source current ISRaising the voltage V at the inverting input of the operational amplifier-It will be reduced. From the formula (5), V at this timeOUTWill also decrease, the gate voltage V is pulled downGIs such that its corresponding source current ISAnd decreases. The above trend can be summarized when the whole negative feedback is not established as the source current ISAt a constant increase, the gate voltage VGIs continuously reduced in absolute value in this trend until the current rises to the gate voltage VGMatching will make the whole negative feedback circuit levelAnd (5) weighing. Gate voltage V when reaching balanceGAccording to the model number and V of the PMOS tubeSETIs determined.
From the above analysis, when the negative feedback is balanced, the output voltage V of the operational amplifier is large because the open-loop gain k of the operational amplifier is a large valueOUTIn the application, the voltage of the inverting input terminal of the operational amplifier is in the range of 5V to 10V, so that the voltage of the inverting input terminal of the operational amplifier is approximately equal to the voltage of the inverting input terminal of the operational amplifier, namely VSETThe value of (c). This is the phenomenon of virtual short and virtual break that we often apply in negative feedback analysis of the operational amplifier. The source current at this time is:
the gate current I is known from the characteristics of PMOS tubeGVery small, for example model IRF9610, with a gate current IGThe maximum is only 100nA, so that the source current I can be generally consideredSAnd a drain current IDApproximately equal, the current through the sampling resistor is approximately equal to the current through the laser diode. The voltage relation of a source electrode, a grid electrode and a drain electrode of the P-type MOS tube is as follows:
VS＜VG＜VD (7)
the voltage relationship is just opposite to that of the N-type MOS tube, so that the voltage V between the grid electrode and the source electrode of the P-type MOS tube is knownGSNegative, the condition for reaching the constant current region being the gate-source voltage VGSIs greater than the absolute value of the threshold voltage.
As can be seen from the above, the source voltage of the PMOS transistor is:
VS＝VCC-IS×RS (8)
from the above formula, the source voltage VSMost of the noise in the signal comes from the power supply V of the operational amplifierCCAnd the noise is VCCAnd (5) common mode. V of reference source output composed of reference source chip LM399 and Berns potentiometer combined with the above knowledgeSETMost of the noise of (2) and VCCIs detected. From the formula (8)The final constant current output can be VCCAnd VSETThe common mode noise in (1) is removed, leaving a small portion of differential mode noise. Therefore, the constant current source circuit based on the P-type MOS tube design can skillfully remove the voltage from the power supply V by using a common mode methodCCThe noise of (2).
The constant current source module designed at this time is a narrow linewidth semiconductor laser for driving a cold atom interferometer, and the laser needs an external PID circuit to lock the output of the whole laser on a specific frequency. In the driving of semiconductor lasers, the most convenient and simplest method is to lock the drive current of the laser, which has certain requirements on the bandwidth. In a common constant current source design, the scan current signal and the output current control signal are output through an operational amplifier to superimpose a scan signal on the output current. However, this design can only suppress the output noise of the constant current source by suppressing the bandwidth down to the order of hundreds of hertz, which results in too much output noise if the bandwidth is high. The constant current source of the present embodiment directly outputs the scanning current to the drain of the PMOS transistor, so that the high scanning bandwidth can be maintained even when the bandwidth of the control output signal is sufficiently reduced.
The scan input module of the present embodiment adopts the prior art. As shown in fig. 5 to 6, the scan input module is formed by a VI conversion circuit formed by two operational amplifiers, and an ultra-low noise operational amplifier is selected, and the scan current range is 10mA, which can well meet the frequency locking requirement of the narrow-linewidth semiconductor laser for the cold atom interferometer.
The scan circuit can be simplified to the circuit shown in fig. 6 for analysis according to the analysis method of the virtual short break of the negative feedback operational amplifier circuit as shown in fig. 5. Wherein R1 resistance is 2K omega, the other resistance is 1K omega, the virtual short break theorem of operational amplifier is applied, and the voltage is V1Has a junction point and a voltage of VINThe node sequence KCL (kirchhoff's current law) yields the following relation:
the combined type (6) and (7) are simplified and can be obtained:
from the above formula (8), the current I is output1The current I is only related to the input voltage, when the input voltage is in the range of-10V to 10V1The variable range of (2) is-1 mA to 1mA, and the adjustable range is one percent of the output current when the constant current output is relative to 100 mA.
As shown in the test result of fig. 7, the test result of the long-term stability of the embodiment is good and has a value of popularization and application, as obtained from the experimental data.
Compared with the traditional constant current source, the embodiment has the following advantages:
(1) the constant current source circuit adopts a design mode of a suspended ground, couples most of noise into a ground plane, isolates the ground from all control signals and power supply of key devices, removes the influence of the ground noise on output current, and effectively reduces the output noise of the constant current source.
(2) The common mode processing is carried out on most of noise in the constant current source power supply voltage and the current setting voltage in the reference source related to the output current of the constant current source, and then the two signals are subtracted to remove most of noise, so that the circuit noise is suppressed to the greatest extent.
(3) The scanning input port is separated from the negative feedback circuit, and most of noise in the negative feedback circuit is filtered by a low-pass filter with cut-off frequency as low as dozens of hertz under the condition of not influencing the bandwidth of the scanning input port.
Therefore, the constant current source has low current noise, extremely high direct current stability and high-speed modulation capability. The design idea of a suspended ground is skillfully used, and most of noise is coupled into the ground; removing common-mode noise by adopting a common-mode denoising mode; and moreover, a power supply system with extremely high denoising capability is designed, a filter circuit is optimized, key devices are carefully selected, and the output noise of the constant current source is reduced to a great extent.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (8)
1. A driving current source of a narrow-linewidth semiconductor laser for a cold atom gyroscope is characterized by comprising a power supply module, a negative feedback module and a scanning input module which are sequentially connected, wherein the power supply module comprises a first-stage linear voltage stabilizer and a second-stage linear voltage stabilizer which are connected in series,
the input end of the first-stage linear voltage stabilizer is connected with the power supply, and the negative voltage output end of the first-stage linear voltage stabilizer is connected with the negative feedback module and is used for suppressing noise from the power supply and providing multiple paths of positive voltage and negative voltage after first-stage conversion;
the input of the second-stage linear voltage stabilizer is connected with the positive voltage output end of the first-stage linear voltage stabilizer, and the output of the second-stage linear voltage stabilizer is connected with the negative feedback module and the scanning input module and is used for further reducing the noise of output current and providing voltage after second-stage conversion;
the negative feedback module is connected with the output of the second-stage linear voltage stabilizer and is used for sampling the output voltage of the second-stage linear voltage stabilizer, calculating the output voltage with a set reference voltage and controlling to output a constant current signal, wherein the reference voltage is referred to the output of the second-stage linear voltage stabilizer;
the negative feedback module comprises an operational amplifier, a reference source, a sampling resistor and a PMOS (P-channel metal oxide semiconductor) tube, wherein the source electrode of the PMOS tube is connected with the output of the second-stage linear voltage stabilizer, the drain electrode of the PMOS tube is grounded after being connected with a load in series, and the grid electrode of the PMOS tube is connected with the output end of the operational amplifier; the sampling resistor is arranged between the output of the second-stage linear voltage stabilizer and the source electrode of the PMOS tube, and the sampling resistor is connected with the reverse input end of the operational amplifier; the same-direction input end of the operational amplifier is connected with the output end of the reference source, and the power supply input end of the operational amplifier is connected with the output of the first-stage linear voltage stabilizer; the anode of the reference source is connected with the output of the second-stage linear voltage stabilizer, the cathode of the reference source is connected with the negative voltage output end of the first-stage linear voltage stabilizer, and the reference voltage is arranged on the reference source;
the scanning input module and the output of the negative feedback module are connected in parallel to a load and used for superposing a scanning current signal on the constant current signal so as to lock the frequency of the constant current signal.
2. The driving current source of a narrow-linewidth semiconductor laser for a cold atomic gyroscope as claimed in claim 1, wherein the reference source comprises a voltage regulator tube and a potentiometer connected in parallel, a cathode of the voltage regulator tube and an anode of the potentiometer are connected in parallel to an output of the second-stage linear voltage regulator, an anode of the voltage regulator tube and a cathode of the potentiometer are connected in parallel and then connected with a negative voltage output end of the first-stage linear voltage regulator through a pull-down resistor, and an output end of the potentiometer is connected with a same-direction input end of the operational amplifier.
3. The driving current source of a narrow linewidth semiconductor laser for a cold atom gyroscope as claimed in claim 1, wherein a feedback coefficient conditioning circuit is provided between the sampling resistor and the inverting input terminal of the operational amplifier.
4. The driving current source of a narrow linewidth semiconductor laser for a cold atom gyroscope of claim 1, wherein the source of the PMOS transistor is further provided with an equal proportion monitoring circuit for monitoring an equal proportion voltage signal of the source of the PMOS transistor.
5. The driving current source of a narrow linewidth semiconductor laser for a cold atom gyroscope of claim 1, wherein the drain of the PMOS transistor is provided with a filter circuit, and the filter circuit is arranged between the drain of the PMOS transistor and the scan input module.
6. The driving current source of a narrow linewidth semiconductor laser for a cold atom gyroscope of claim 1, wherein the first stage linear regulator comprises two power conversion modules in parallel, one of the power conversion modules is configured to convert a positive power input into a first stage positive voltage output, and the other power conversion module is configured to convert a negative power input into a first stage negative voltage output.
7. The narrow linewidth semiconductor laser drive current source of claim 6, wherein the second stage linear regulator is configured to convert the first stage positive voltage output to a second stage positive voltage output.
8. The driving current source of a narrow linewidth semiconductor laser for a cold atom gyroscope as claimed in claim 1, further comprising a protection circuit, wherein the protection circuit comprises a protection diode arranged in forward bias, an anode of the protection diode is connected to a current input terminal of the load, a cathode of the protection diode is grounded, and a forward conduction voltage drop of the protection diode is higher than a forward conduction voltage drop of the load.
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| CN109326956A (en) * | 2018-11-19 | 2019-02-12 | 深圳市大族锐波传感科技有限公司 | A kind of laser driving system and semiconductor laser module |
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