CN113050742B - Precise constant current source circuit - Google Patents
Precise constant current source circuit Download PDFInfo
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- CN113050742B CN113050742B CN202110265917.4A CN202110265917A CN113050742B CN 113050742 B CN113050742 B CN 113050742B CN 202110265917 A CN202110265917 A CN 202110265917A CN 113050742 B CN113050742 B CN 113050742B
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
- G05F1/10—Regulating voltage or current
- G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
- G05F1/56—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices
- G05F1/565—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor
- G05F1/567—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor for temperature compensation
Abstract
A precise constant current source circuit belongs to the technical field of radio frequency microwave. The method comprises the following steps: the lifting voltage power supply chip with the lifting voltage function comprises a power supply input filter capacitor, a divider resistor, a feedback circuit, a power supply output filter capacitor, a load, a microprocessor with an ADC (analog to digital converter) module and a digital potentiometer, wherein the feedback circuit comprises a sampling resistor and an operational amplifier. Compared with the traditional constant current source circuit, the precise constant current source circuit has the advantages of simple implementation mode and high current precision, and can achieve the purpose of quick jump of the current required by the radio frequency microwave chip; meanwhile, different current outputs are controlled through the microprocessor, current limit protection is achieved, and the requirement of a more universal constant current source can be met.
Description
Technical Field
The invention belongs to the technical field of radio frequency microwaves, and particularly relates to a precise constant current source circuit applied to a radio frequency microwave control circuit.
Background
A constant current source is a power source capable of supplying a constant current to various loads, and is a widely used component. Fig. 1 is a constant current source circuit in the prior art, which includes a power MOS transistor Q11, two voltage dividing resistors R11 and R12, two operational amplifiers U11 and U12, a sampling resistor R13, and a voltage source VCC, and the circuit realizes setting of different voltages through the two voltage dividing resistors R11 and R12 based on a linear power supply, and calculates a current flowing through a load by detecting a voltage on the sampling resistor R13 through a voltmeter, so as to realize a constant current.
Fig. 2 is another prior art constant current source circuit, which includes a power MOS transistor Q21, a microprocessor U21 with ADC and DAC functions, two operational amplifiers U22 and U23, a sampling resistor R21, and a voltage source VCC. The working principle is as follows: the current flowing through the load passes through a power MOS transistor Q21 and a sampling resistor R21, the sampling resistor R21 converts a current signal into an analog voltage signal, the analog voltage signal is connected with the inverting input end of an operational amplifier U22, the microprocessor U21 outputs the analog voltage of an internal digital-to-analog converter to the non-inverting input end of the operational amplifier U22 through a preset digital signal, when the voltage of the non-inverting input end V + of the operational amplifier U22 is higher than that of the inverting input end V-, the power supply voltage is output, and when the voltage of the non-inverting input end V + of the operational amplifier U22 is lower than that of the inverting input end V-, the zero voltage is output. The operational amplifier U22 controls the conduction of the power MOS transistor Q21 by comparing the voltages of the two input terminals until the analog voltage V23 output by the sampling resistor R21 approaches the voltage V21 output by the microprocessor U21 through the internal digital-to-analog converter, that is, the voltage of the sampling resistor R21 does not change, and the current flowing through the load does not change. Although the scheme can reduce the accuracy and the temperature stability generated by resistance voltage division, the constant current source required by high-precision large current cannot be well met.
Most of common constant current source circuits in the market at present adopt discrete devices, voltage feedback signals are input through an inverting input end of an operational amplifier, a reference voltage source or a DAC (digital-to-analog converter) of an MCU (micro-programmed control unit) is used for giving reference voltage to a non-inverting end of the operational amplifier, and the constant current source realized by the method is greatly influenced by temperature, low in current precision, low in reliability and small in driving current.
Disclosure of Invention
The invention aims to provide a precise constant current source circuit aiming at the defects in the background technology.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a precision constant current source circuit, comprising:
a lifting voltage power supply chip U1 with a lifting voltage function;
the power input filter capacitor C1 is connected with the input end Vin and the common ground end GND of the lifting voltage power supply chip;
a voltage dividing resistor R1, wherein a first input end and a second input end of the voltage dividing resistor R1 are respectively connected with an output end Vout and a feedback end FB of the buck-boost power supply chip, and the voltage of the output end Vout of the buck-boost power supply chip is represented by VOUT;
the feedback circuit comprises a sampling resistor R3 and an operational amplifier U2, one end of the sampling resistor R3 is connected with the output end Vout of the lifting voltage power supply chip, the other end of the sampling resistor R3 is connected with the power supply output filter capacitor C2, and the current flowing through the sampling resistor R3 is represented by IO; a first input end V + and a second input end V-of the operational amplifier U2 are respectively connected with two ends of a sampling resistor R3;
One end of the power output filter capacitor C2 is connected with the sampling resistor R3, and the other end of the power output filter capacitor C2 is connected with a common ground end GND;
one end of the load RS is connected with the sampling resistor R3, and the other end of the load RS is connected with a common ground end GND;
the microprocessor U3 is internally provided with an ADC module, an analog input pin ADC of the microprocessor U3 is connected with an output end of the operational amplifier, and an analog voltage output by the output end of the operational amplifier is represented by VO;
a digital potentiometer R2, wherein a first input end A of the digital potentiometer R2 is connected with a second input end of the voltage dividing resistor R1, and a second input end W of the digital potentiometer R2 is connected with a common ground end GND; the control clock terminal SCL of the digital potentiometer is connected with the control clock terminal SCL of the microprocessor U3, and the control data terminal SDA of the digital potentiometer is connected with the control data terminal SDA of the microprocessor U3.
The microprocessor U3 has an ADC module therein, and can collect analog voltage generated by the operational amplifier U2, and the microprocessor U3 can perform serial communication control with the digital potentiometer R2.
The operational amplifier U2 can amplify the analog voltage generated by the sampling resistor R3, so that the output voltage is within the range allowed by the ADC module of the microprocessor.
The invention provides a precise constant current source circuit, which has the working principle that:
after initial power-on, presetting a required initial current value IOSET and an allowed error value delta in the microprocessor, converting the initial current value IOSET into a resistance value corresponding to the digital potentiometer R2, transmitting the resistance value to the digital potentiometer R2, and changing the resistance value of the digital potentiometer R2 according to received data;
adjusting the resistance of the digital potentiometer to R2 0 The lifting voltage power chip U1 is based on voltage dividing resistor R1 and digital potentiometer R2 0 The output voltage VOUT is obtained according to the ratio, the generated current IO flows through R3 and RS, then the voltage at two ends of R3 is collected and amplified through an operational amplifier U2, the voltage is transmitted to a microprocessor U3 with an ADC module, and the transmitted voltage signal is represented by VO; the microprocessor U3 converts the voltage VO into a corresponding current value IO, the IO and the IOSET are compared through the microprocessor U3, and when the absolute value of the difference between the IO and the IOSET is smaller than a preset delta value, the set current value and the actual current value meet the precision requirement, and the purpose of high-precision constant current is achieved.
When the absolute value of the difference between the current value and the actual current value is larger than a preset delta value, the set current value and the actual current value do not meet the precision requirement, at the moment, if IO is larger than IOSET and the actual current value is larger than the set current value, data are sent to a digital potentiometer R2 through a microprocessor U3, the output voltage VOUT is reduced by increasing the resistance value of R2, and IO is further reduced until the requirement of | IO-IOSET | < delta is met; if IO < IOSET indicates that the actual current value is smaller than the set current value, the microprocessor sends data to the digital potentiometer R2, the resistance value of R2 is reduced, the output voltage VOUT is increased, IO is further increased until | IO-IOSET | < delta is met, and therefore the purpose of precise constant current is achieved.
Compared with the prior art, the invention has the following beneficial effects:
1. compared with the traditional constant current source circuit, the precise constant current source circuit has the advantages of simple implementation mode and high current precision, and can achieve the purpose of requiring the rapid jump of the current of the radio frequency microwave chip.
2. The invention can control different current outputs through the microprocessor, has current limit protection and can realize the requirement of a more universal constant current source.
3. The invention can control large current and small current in different degrees, and meets specific requirements by selecting different buck-boost power chips.
4. The buck-boost power supply chip is adopted, the input voltage range is large, and the buck-boost power supply chip has more advantages compared with the conventional large-voltage input constant current source circuit.
5. The constant current source circuit of the invention can change the current value rapidly through the microprocessor without changing the hardware circuit.
Drawings
Fig. 1 is a circuit diagram of a constant current source provided in the prior art;
fig. 2 is a circuit diagram of a constant current source provided in another prior art;
fig. 3 is a circuit of a precise constant current source according to the present invention;
fig. 4 is a schematic diagram of a constant current source circuit according to an embodiment of the present invention.
Detailed Description
The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown and described, and in which embodiments of the invention can be better understood and practiced.
The constant current source circuit based on the digital potentiometer and the lifting piezoelectric source chip, provided by the invention, has the advantages that an FB pin of the lifting piezoelectric source chip U1 is connected with an A pin of the digital potentiometer R2, and is simultaneously connected with a second input end of the sampling resistor R1, serial data are sent to the digital potentiometer R2 through the microprocessor U3, the resistance value of the digital potentiometer R2 is changed, further, the output VOUT of different voltages of the lifting piezoelectric source chip is realized in a resistor voltage division mode, and the output current is precisely collected through a feedback circuit and a load RS which are connected at the back, so that precise constant current is realized.
The buck-boost power supply chip adopted by the invention has high output stability and high output power, and is combined with a high-precision resistor to obtain a constant current source circuit which has high output precision, good adjustability, quick output change, large output current and perfect protection and control functions.
Examples
FIG. 3 is a circuit diagram of the constant current source of the present invention, which specifically describes the input Vin, output Vout, feedback FB, and common GND of the buck-boost power chip U1 in the regulation circuit, wherein the input of the buck-boost power chip U1 The pin Vin is connected with a power supply VCC, the output is represented by VOUT, and after passing through a sampling resistor R3, the output voltage is represented by VS, wherein RS is a load. The control clock pin of the digital potentiometer R2 is SCL, the control data pin is SDA, the control clock end SCL of the microprocessor U3 is connected with the control clock end SCL of the digital potentiometer R2, the control data end SDA of the microprocessor U3 is connected with the data control end SDA of the digital potentiometer R2, and the communication mode adopts I 2 Protocol C, the fastest speed can reach 400 kHz. The pin W of the digital potentiometer R2 is connected to GND, and the pin A is connected to the feedback FB of the buck-boost chip U1, so that the digital potentiometer is used as a resistor R2.
R1 and R2 are feedback divider resistors, wherein R2 is a digital potentiometer, and has 1024-bit resolution and extremely low temperature coefficient. The R1 and the R2 are connected with the buck-boost power supply chip U1 through an FB pin and are compared with the internal reference voltage VREF, the comparison result is sent to the serial data control digital potentiometer R2 through the microprocessor U3, and the output voltage VOUT is further changed by changing the resistance value of the digital potentiometer R2. The relationship of the output voltage VOUT with R1 and R2 satisfies the following equation:
VOUT＝(R1/R2+1)*VREF
r3 is a low-temperature drift precision resistor, and the constant current IO is determined by connecting with a load resistor RS, and the relationship is as follows:
IO＝VOUT/(R3+RS)
The feedback circuit is through connecting operational amplifier U2 with the both ends of sampling resistance R3, convert the electric current IO that sampling resistance R2 flows into analog voltage, analog voltage amplifies the back through operational amplifier U2, output VO to microprocessor U3, microprocessor U3 converts analog voltage VO into digital voltage through inside ADC module from taking to current value IO that the VO corresponds is obtained in the calculation, compare IO and IOSET through microprocessor U3:
when the absolute value of the difference between the two is smaller than a preset delta value, the set current value and the actual current value meet the precision requirement, and the purpose of high-precision constant current is achieved.
When the absolute value of the difference between the two is greater than a preset value delta, the microprocessor U3 sends data to the digital potentiometer R2, the value of R2 is changed, the output voltage VOUT is further changed, and the current IO is changed, until the difference between the set current value and the actual current value is less than the preset value delta, the microprocessor U3 stops sending data to the digital potentiometer R2, the value of R2 is made to be constant, and the output voltage VOUT is further constant, and the output voltage VOUT is also constant. Specifically, if IO > IOSET, indicating that the actual current value is greater than the set current value, the microprocessor U3 sends data to the digital potentiometer R2, and by increasing the resistance value of R2, the output voltage VOUT is reduced, and then IO is reduced until | IO-IOSET | < Δ is satisfied; if IO < IOSET indicates that the actual current value is smaller than the set current value, the microprocessor sends data to the digital potentiometer R2, the resistance value of R2 is reduced, the output voltage VOUT is increased, IO is further increased until | IO-IOSET | < delta is met, and therefore the purpose of precise constant current is achieved.
More specifically, the voltage VO collected by the microprocessor U3 is obtained by scaling, i.e., IO — VO/(R3 × M), M is the amplification factor of the operational amplifier U2,
in the embodiment, the microprocessor adopts a singlechip STM32F103C8T 6; the boost-buck power supply chip selects LM34936, and the input voltage only needs 6V; the operational amplifier selects a high-precision zero drift current detection amplifier INA 240; the sampling resistor is a low-temperature-drift precision resistor; the digital potentiometer selects X9C104, and the output power of 80W at most can be realized through control.
The above-described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Claims (3)
1. A precision constant current source circuit, comprising:
a lifting voltage power supply chip with a lifting voltage function;
the power input filter capacitor is connected with the input end and the common ground end of the lifting piezoelectric power chip;
the first input end and the second input end of the divider resistor are respectively connected with the output end and the feedback end of the buck-boost power supply chip;
The feedback circuit comprises a sampling resistor and an operational amplifier, wherein one end of the sampling resistor is connected with the output end of the lifting piezoelectric power chip, and the other end of the sampling resistor is connected with the power output filter capacitor; the first input end and the second input end of the operational amplifier are respectively connected with two ends of the sampling resistor;
one end of the power output filter capacitor is connected with the sampling resistor, and the other end of the power output filter capacitor is connected with the common ground end;
one end of the load is connected with the sampling resistor, and the other end of the load is connected with the common ground end;
the microprocessor is internally provided with an ADC module, and an analog input pin of the microprocessor is connected with the output end of the operational amplifier;
the first input end of the digital potentiometer is connected with the second input end of the divider resistor, and the second input end of the digital potentiometer is connected with the common ground end; the control clock end of the digital potentiometer is connected with the control clock end of the microprocessor, and the control data end of the digital potentiometer is connected with the control data end of the microprocessor;
after initial power-on, presetting a required initial current value IOSET and an allowed error value delta in a microprocessor, converting the initial current value IOSET into a resistance value corresponding to a digital potentiometer, and transmitting the resistance value to the digital potentiometer R2, wherein the digital potentiometer changes the resistance value thereof according to received data;
Adjusting resistance of digital potentiometer to R2 0 The buck-boost power supply chip is connected with the digital potentiometer R2 according to the voltage dividing resistor R1 0 The output voltage VOUT is obtained according to the ratio, the generated current IO flows through the sampling resistor R3 and the load RS, then the voltage at two ends of the sampling resistor R3 is collected and amplified through the operational amplifier U2, the voltage is transmitted to the microprocessor U3 with the ADC module, and the transmitted voltage signal is represented by VO; the microprocessor U3 converts the voltage VO into a corresponding current value IO, the IO and the IOSET are compared through the microprocessor U3, and when the absolute value of the difference between the IO and the IOSET is smaller than a preset delta value, the set current value and the actual current value meet the precision requirement;
when the absolute value of the difference between the current value and the actual current value is larger than a preset delta value, the set current value and the actual current value do not meet the precision requirement, at the moment, if IO is larger than IOSET and the actual current value is larger than the set current value, data are sent to a digital potentiometer R2 through a microprocessor U3, the output voltage VOUT is reduced by increasing the resistance value of R2, and IO is further reduced until the requirement of | IO-IOSET | < delta is met; if IO < IOSET, indicating that the actual current value is less than the set current value, the microprocessor sends data to the digital potentiometer R2, and by decreasing the resistance value of R2, the output voltage VOUT is increased, and then IO is increased until | IO-IOSET | < Δ is satisfied.
2. The precise constant current source circuit of claim 1, wherein the microprocessor is internally provided with an ADC module for collecting analog voltage generated by the operational amplifier and performing serial communication control with the digital potentiometer.
3. The precise constant current source circuit of claim 1, wherein the operational amplifier amplifies the analog voltage generated by the sampling resistor to make the output voltage within the range allowed by the microprocessor ADC module.
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| CN113659804B (en) * | 2021-08-13 | 2023-06-06 | 上海空间电源研究所 | System for restraining drift amount of high-low temperature constant current point for aerospace |
| CN115480612A (en) * | 2022-01-25 | 2022-12-16 | 中国船舶重工集团公司第七0七研究所 | Ultra-high stability bipolar current source circuit adaptive to wide-temperature environment |
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| CN103037572A (en) * | 2012-11-09 | 2013-04-10 | 深圳硕日新能源科技有限公司 | Solar light-emitting diode (LED) wireless control constant-current all-in-one machine controller |
| CN104122924A (en) * | 2014-07-18 | 2014-10-29 | 苏州华兴源创电子科技有限公司 | Switch-type voltage stabilizing circuit and constant voltage constant current generation circuit with switch-type voltage stabilizing circuit |
| CN207249525U (en) * | 2017-10-20 | 2018-04-17 | 博众精工科技股份有限公司 | A kind of controllable constant current source circuit |
| CN211697923U (en) * | 2019-12-31 | 2020-10-16 | 珠海市运泰利自动化设备有限公司 | High-precision constant-resistance analog load adjusted through program-controlled digital potentiometer |
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| TWI277851B (en) * | 2005-02-25 | 2007-04-01 | Winbond Electronics Corp | Adjustable regulated power device |
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| CN103037572A (en) * | 2012-11-09 | 2013-04-10 | 深圳硕日新能源科技有限公司 | Solar light-emitting diode (LED) wireless control constant-current all-in-one machine controller |
| CN104122924A (en) * | 2014-07-18 | 2014-10-29 | 苏州华兴源创电子科技有限公司 | Switch-type voltage stabilizing circuit and constant voltage constant current generation circuit with switch-type voltage stabilizing circuit |
| CN207249525U (en) * | 2017-10-20 | 2018-04-17 | 博众精工科技股份有限公司 | A kind of controllable constant current source circuit |
| CN211697923U (en) * | 2019-12-31 | 2020-10-16 | 珠海市运泰利自动化设备有限公司 | High-precision constant-resistance analog load adjusted through program-controlled digital potentiometer |
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