CN115347896B - High-precision DC signal source - Google Patents
High-precision DC signal source Download PDFInfo
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- CN115347896B CN115347896B CN202211264987.9A CN202211264987A CN115347896B CN 115347896 B CN115347896 B CN 115347896B CN 202211264987 A CN202211264987 A CN 202211264987A CN 115347896 B CN115347896 B CN 115347896B
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
- H03M1/00—Analogue/digital conversion; Digital/analogue conversion
- H03M1/10—Calibration or testing
- H03M1/1071—Measuring or testing
- H03M1/109—Measuring or testing for dc performance, i.e. static testing
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- H—ELECTRICITY
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- H03K7/08—Duration or width modulation ; Duty cycle modulation
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Abstract
The invention discloses a high-precision DC signal source, which comprises: the device comprises a main control MCU processor, an integrating circuit, a low-pass filter circuit and an analog-to-digital converter; the channel of the analog-to-digital converter is connected with the output end of the integrating circuit and is used for receiving the first output voltage output by the integrating circuit; a second channel of the analog-to-digital converter is connected with the output end of the low-pass filter circuit and used for receiving a second output voltage output by the low-pass filter circuit; the analog-to-digital converter converts the first output voltage and the second output voltage into digital quantity and then sends the digital quantity to the main control MCU processor; the main control MCU processor calculates a PWM value according to the output of the analog-to-digital converter and outputs a PWM signal; the integrating circuit integrates the PWM signal to obtain a new first output voltage; the low-pass filter circuit processes the new first output voltage to obtain a new second output voltage; the signal source can output a high-precision stable and adjustable direct current signal.
Description
Technical Field
The invention belongs to the technical field of signal sources, and particularly relates to a high-precision DC signal source.
Background
In the test items of analog-to-digital converters (ADCs), that is, in the dc parametric test, there are many dc signal sources that need to be used with high precision, such as: positive and negative full-scale voltage errors, non-linearity of conversion, direct current gain errors, and the like. For example, a 16-bit ADC with a full scale of 10V (digital coding 0-65535 means 0-10V), requires a 10V DC signal during production test and calibration, and the error can not exceed 10V/65536, i.e. 10V +/-70 uV. This parameter is generally difficult to satisfy by both ATE tools and dc power supplies. Therefore, it is important to output a dc signal source with adjustable accuracy.
The following schemes exist for the current testing of ADC tributary parameters:
1. most of the methods (source meter systems) use a direct current signal source and a high-precision multimeter, namely, the signal source outputs a relatively stable voltage signal, and then the high-precision voltmeter is used for reading the actual size, so that the defect of output precision is overcome. The method is easy to realize and low in cost. The disadvantage is that the resolution of the signal source is limited, only one near-full scale voltage can be output, and then the voltage meter is used for comparing the ADC to calculate the near-full scale error value.
2. The operational amplifier is used for adding two voltage signals, one is roughly adjusted and the other is finely adjusted. The method is easy to realize and low in cost. The disadvantage is that the operational amplifier itself also has a linearity problem, which is equivalent to introducing errors into the measurement system.
3. And adjusting the duty ratio by using PWM, adding a filter, and outputting an adjustable direct current signal by adjusting the duty ratio. The disadvantages are that the PWM frequency needs to be very high, the output accuracy is greatly affected by the power supply system, and the response speed is very slow even if closed loop dynamic regulation is added.
4. The ADC is tested using the high precision DAC output. Currently, the highest precision DAC is 20 bits, and the output linearity of the DAC is not as good as that of the ADC, if the DAC is used for testing the ADC with more than 16 bits.
Therefore, how to output a high-precision stable and adjustable dc signal for calibrating and testing ADC and other analog semiconductor circuits becomes a key issue in current research.
Disclosure of Invention
In view of the above problems, the present invention provides a high-precision DC signal source that can output a stable and adjustable DC signal with high precision.
The embodiment of the invention provides a high-precision DC signal source, which comprises: the device comprises a main control MCU processor, an integrating circuit, a low-pass filter circuit and an analog-to-digital converter;
a first channel of the analog-to-digital converter is connected with the output end of the integrating circuit and is used for receiving a first output voltage output by the integrating circuit;
a second channel of the analog-to-digital converter is connected with the output end of the low-pass filter circuit and used for receiving a second output voltage output by the low-pass filter circuit;
the analog-to-digital converter, the master control MCU processor, the integrating circuit and the low-pass filter circuit are sequentially connected;
the analog-to-digital converter is used for converting the first output voltage and the second output voltage into digital quantity and then sending the digital quantity to the main control MCU processor;
the master control MCU processor calculates a PWM value according to the output of the analog-to-digital converter and outputs a PWM signal;
the integrating circuit integrates the PWM signal to obtain a new first output voltage;
and the low-pass filter circuit processes the new first output voltage to obtain a new second output voltage.
Further, the main control MCU processor comprises an error numerical value calculation module and a PID closed-loop control calculation module;
the error numerical value calculation module is used for respectively comparing the first output voltage and the second output voltage with a voltage set by a PC (personal computer) to obtain corresponding error values ERR1 and ERR2;
and the PID closed-loop control calculation module is used for calculating based on the error values ERR1 and ERR2 to obtain a PWM value and outputting a PWM signal.
Further, the PID closed-loop control calculation module generates a new PWM value by calculating ERR1 and ERR1 differential ERR1_ D as a first closed loop, calculating ERR2_ I of ERR2 and calculating ERR1 of the first closed loop as a second closed loop, and calculating the first closed loop and the second closed loop at the same time.
Further, the integration circuit performs integration processing on the PWM, specifically: when the duty ratio of the PWM is larger than 50%, the output of the integrating circuit rises; and when the duty ratio of the PWM is less than 50%, the output of the integrating circuit is reduced.
Further, the analog-to-digital converter is a 24-bit AD7175 chip.
Compared with the prior art, the high-precision DC signal source recorded by the invention has the following beneficial effects:
1. the integrator is realized by an integrating circuit, the digital quantity continuity of the analog quantity is better, and therefore the resolution ratio of PWM is not required to be very high (the traditional 16-bit PWM can only output 16-bit resolution ratio, and the 16-bit PWM of the system can also achieve 24-bit resolution ratio through closed-loop control).
2. In the invention, a 24-bit analog-to-digital converter is used as closed-loop sampling, so that the system output can be stabilized at the precision of 24 bits.
3. In general, a closed-loop control system adopts PID control (proportional plus integral plus derivative operation is performed on an error respectively), and then controls a PWM duty ratio, thereby changing an output. The system has two PID loops, two loops are used for calculating PWM at the same time, P and D of ERR1 are calculated by software in PID of the first loop, and I is realized by hardware circuit alone. P and I for ERR2 are calculated by software in the PID of the second loop, and D is obtained from EER1 of the first loop; the above design of the invention can make the whole system stable more quickly.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
fig. 1 is a schematic diagram of a high-precision DC signal source framework according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of a principle of a high-precision DC signal source according to an embodiment of the present invention.
Fig. 3 is a schematic diagram of a sampling circuit of an analog-to-digital converter according to an embodiment of the present invention.
Fig. 4 is a schematic diagram of an integration circuit according to an embodiment of the present invention.
Fig. 5 is a schematic diagram of a low-pass filter circuit according to an embodiment of the present invention.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
Referring to fig. 1 to 5, an embodiment of the present invention provides a high-precision DC signal source, including: the device comprises a main control MCU processor, an integrating circuit (integral), a low pass filter circuit (LPF) and an analog-to-digital converter; the channel of the analog-to-digital converter is connected with the output end of the integrating circuit and used for receiving a first output voltage output by the integrating circuit; a second channel of the analog-to-digital converter is connected with the output end of the low-pass filter circuit and used for receiving a second output voltage output by the low-pass filter circuit; the analog-to-digital converter, the master control MCU processor, the integrating circuit and the low-pass filter circuit are sequentially connected; the analog-to-digital converter is used for converting the first output voltage and the second output voltage into digital quantity and then sending the digital quantity to the main control MCU processor; the main control MCU processor calculates a PWM value according to the output of the analog-to-digital converter and outputs a PWM signal; the integrating circuit integrates the PWM signal to obtain a new first output voltage; the low-pass filter circuit processes the new first output voltage to obtain a new second output voltage.
In the embodiment of the invention, the main control MCU processor comprises an error numerical value calculation module and a PID closed-loop control calculation module; the error value calculation module is used for respectively comparing the first output voltage and the second output voltage with a voltage set by a PC (personal computer) to obtain corresponding error values ERR1 and ERR2; the PID closed-loop control calculation module is used for calculating based on the error values ERR1 and ERR2 to obtain a PWM value and outputting a PWM signal; the method specifically comprises the following steps: the PID closed-loop control calculation module is used for calculating the integral ERR2_ I of ERR2 and taking the ERR1 of the first closed loop as a second closed loop at the same time by calculating the ERR1 and the derivative ERR1_ D of the ERR1 as the first closed loop, and generating a new PWM value.
In the embodiment of the invention, the analog-to-digital converter is a 24-bit AD7175 chip.
When the high-precision DC signal source provided by the embodiment of the invention is applied to calibrate and test the ADC, for example, the signal source of the invention is used for outputting a 10V direct current signal, and the ADC to be tested is used for measuring the direct current signal to obtain a measured value; and assuming that the measured value is 9.5V, readjusting the reference voltage inside the ADC after calculation, and increasing by 0.5V to enable the measured value to be as close to the signal source as possible, thereby realizing calibration and test.
Referring to fig. 2, the working principle of the high-precision DC signal source provided by the embodiment of the present invention is as follows:
step 1: the main control MCU processor sets voltage from the PC and obtains a first output voltage and a second output voltage from the analog-to-digital converter;
and 2, step: the main control MCU calculates ERR1 and ERR2, ERR1_ D and ERR2_ I, PWM1 and PWM2 in turn, and finally PWM is obtained;
and 3, step 3: the integrating circuit performs integration processing on the PWM and outputs a first output voltage; when the duty ratio of the PWM is larger than 50%, the first output voltage rises; when the duty ratio of the PWM is less than 50%, the first output voltage is reduced;
and 4, step 4: the low-pass filter circuit carries out filtering processing on the first output voltage output to output a stable voltage which is recorded as a second output voltage;
and 5: the MCU obtains the first output voltage and the second output voltage from the analog-to-digital converter again; two closed loops are formed;
repeating the steps 1 to 5.
In the step 2, the analog-to-digital converter samples the attenuation voltages (i.e. the first output voltage and the second output voltage) of the integrating circuit and the low-pass filter circuit at the same time, and forms two closed loops, so that the following advantages exist: if only the second output voltage of the low-pass filter circuit is collected, the low-pass filter circuit has larger time delay, and the main control MCU cannot obtain feedback immediately after the PWM is regulated. Resulting in a slow closed loop speed; in the embodiment of the invention, the analog-to-digital converter collects the second output voltage as a second closed loop, collects the first output voltage of the integrating circuit as a first closed loop, innovatively uses the error of the first closed loop as a differential link of the second closed loop, can realize faster prediction of the change direction of the second output voltage, and calculates the actual value of the second output voltage in advance and with higher precision.
In step 3 above, the following benefits exist using a hardware integration circuit: if the software method is used for integration according to a general method, the output has a large discrete type, and the output has continuity by using a hardware integration circuit.
In step 4 above, the use of a low pass filter circuit has the following benefits: due to the relatively severe sawtooth wave and system noise of the first output voltage of the integrating circuit, the filtering of the low-pass filter circuit needs to be added.
In the above step 5, the second output voltage is sampled to form the second closed loop, and the following advantages exist: although the loop response speed is high when only the first output voltage is sampled for closed-loop control, the second output voltage cannot be obtained actually because offset voltage exists in the low-pass filter circuit. The second output voltage is sampled back to form a second closed loop, so that the precision of the output voltage can be improved;
the first closed loop and the second closed loop are distinguished as follows: the first closed loop has high response speed and low precision; the second closed loop has low response speed and high precision. By calculating the two loops and taking the error of the first loop as the differential of the second loop, the stability of the loops can be improved, and the total loop has the characteristics of high response speed and high precision
The embodiment of the invention provides a high-precision DC signal source, and the convergence time of a system is faster and the stability is improved through hardware integration, software proportion and differential calculation and a cross-controlled double-loop design.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (5)
1. A high accuracy DC signal source, comprising: the device comprises a main control MCU processor, an integrating circuit, a low-pass filter circuit and an analog-digital converter;
a first channel of the analog-to-digital converter is connected with the output end of the integrating circuit and is used for receiving a first output voltage output by the integrating circuit;
a second channel of the analog-to-digital converter is connected with the output end of the low-pass filter circuit and used for receiving a second output voltage output by the low-pass filter circuit;
the analog-to-digital converter, the master control MCU processor, the integrating circuit and the low-pass filter circuit are sequentially connected;
the analog-to-digital converter is used for converting the first output voltage and the second output voltage into digital quantity and then sending the digital quantity to the main control MCU processor;
the master control MCU processor calculates a PWM value according to the output of the analog-to-digital converter and outputs a PWM signal;
the integrating circuit integrates the PWM signal to obtain a new first output voltage;
and the low-pass filter circuit processes the new first output voltage to obtain a new second output voltage.
2. The high accuracy DC signal source of claim 1, wherein the master MCU processor comprises an error value calculation module and a PID closed loop control calculation module;
the error value calculation module is used for comparing the first output voltage and the second output voltage with a voltage set by a PC respectively to obtain corresponding error values ERR1 and ERR2;
and the PID closed-loop control calculation module is used for calculating based on the error values ERR1 and ERR2 to obtain a PWM value and outputting a PWM signal.
3. The high accuracy DC signal source of claim 2, wherein the PID closed loop control calculation module generates new PWM values by calculating ERR1 and ERR1 differential ERR1_ D as a first closed loop, by calculating ERR2, ERR2 integral ERR2_ I of ERR2 and by calculating ERR1 of the first closed loop as a second closed loop, simultaneously for the first closed loop and the second closed loop.
4. The high-precision DC signal source according to claim 1, wherein the integrating circuit integrates the PWM, and specifically comprises: when the duty ratio of the PWM is larger than 50%, the output of the integrating circuit rises; and when the duty ratio of the PWM is less than 50%, the output of the integrating circuit is reduced.
5. The high accuracy DC signal source of claim 1, wherein the analog-to-digital converter is a 24-bit AD7175 chip.
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Citations (4)
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|---|---|---|---|---|
| US5130565A (en) * | 1991-09-06 | 1992-07-14 | Xerox Corporation | Self calibrating PWM utilizing feedback loop for adjusting duty cycles of output signal |
| JP2005285476A (en) * | 2004-03-29 | 2005-10-13 | Iiyama Corp | Inverter device |
| CN105843282A (en) * | 2016-03-23 | 2016-08-10 | 武汉光迅科技股份有限公司 | Temperature control device and temperature control method based on FPGA for optical amplifier |
| CN210881607U (en) * | 2019-08-16 | 2020-06-30 | 上海福太隆汽车电子科技有限公司 | Control circuit of external control variable-discharge compressor on air conditioner controller in automobile |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8879988B2 (en) * | 2012-12-19 | 2014-11-04 | Cambridge Silicon Radio Limited | Receiver for a telecommunications system |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5130565A (en) * | 1991-09-06 | 1992-07-14 | Xerox Corporation | Self calibrating PWM utilizing feedback loop for adjusting duty cycles of output signal |
| JP2005285476A (en) * | 2004-03-29 | 2005-10-13 | Iiyama Corp | Inverter device |
| CN105843282A (en) * | 2016-03-23 | 2016-08-10 | 武汉光迅科技股份有限公司 | Temperature control device and temperature control method based on FPGA for optical amplifier |
| CN210881607U (en) * | 2019-08-16 | 2020-06-30 | 上海福太隆汽车电子科技有限公司 | Control circuit of external control variable-discharge compressor on air conditioner controller in automobile |
Non-Patent Citations (1)
| Title |
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| 一种新型的高精度Sigma_Delta调制器结构;王阁藩等;《电子测量技术》;20220630;第45卷(第12期);第1-5页 * |
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