Power supply adjusting equipment and voltage-adjustable power supply circuit thereof

Abstract

The invention provides a power supply regulating device and a voltage-adjustable power supply circuit thereof, and relates to the technical field of power supply regulation, the circuit is additionally provided with a sampling resistor, an operational amplifier unit and an MCU on the basis of keeping the original sampling partial voltage, and adjustable analog level output by the MCU is injected into a DC-DC feedback pin after being subjected to operational amplifier gain, so that the voltage-adjustable power supply circuit is formed. The potential of a feedback node is biased in a voltage superposition mode, so that the output voltage and the analog level are in an approximately linear relation; according to the invention, higher resolution adjustment can be obtained in a preset full range only by changing the DAC level or the PWM duty ratio, the gear intervals are uniform, digital potentiometers or segmented switching are not needed, the calculation is simple, the hardware cost is low, and the control is convenient. The high-precision power supply can be widely applied to occasions requiring a software controllable high-precision power supply, such as a thermal printing head test fixture, ink-jet head ink quantity control, motor torque adjustment and the like. The invention aims to solve the problems that the resolution of a low-voltage section is suddenly reduced and the fineness is insufficient due to resistance-voltage nonlinearity during wide-range voltage regulation of a traditional digital potentiometer type DC-DC feedback network.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power supply regulation, in particular to a power supply regulation device and a voltage-adjustable power supply circuit thereof. BACKGROUND

[0002] In some tooling jigs, a power supply circuit that can be flexibly adjusted by software is often needed. For example, in the application scenarios of thermal printhead (TPH) test jigs, ink volume control of inkjet printheads, torque adjustment control of motors, etc., because a certain index of the device under test, such as the resistance value of the TPH, the ink volume of the printhead, the torque of the motor, etc., is directly related to the supply voltage.

[0003] Taking the thermal printhead test jig as an example, on the thermal printhead test jig of the thermal printer, it is necessary to test and correct the resistance value of TPHs of different voltage specifications, and it is often necessary to continuously adjust the output of the DC power supply in the range of 3 V~40 V by 0.1 V or even finer steps through software to supply power to the TPH, and the full-range accuracy is better than 1%.

[0004] To realize such a voltage-adjustable power supply circuit, the traditional approach is to first select a stable input power supply, such as 24V or 48V, and then select a suitable power supply topology according to the range of the output voltage to build a DC-DC power conversion circuit, such as boost, buck, buck-boost, etc. Further, the output voltage of the DC-DC power conversion circuit is generally adjusted through a feedback circuit, so the software control of the output voltage is generally achieved by changing the resistance of the feedback loop; wherein the input voltage Vin is converted to the output voltage Vout through the DC-DC power supply circuit module, in a general DC-DC power supply circuit module, the feedback circuit is composed of sampling resistors r1 and r2, assuming that the feedback reference voltage of the power supply circuit is Vref, then the expression of the output voltage is: Vout=Vref*(1+r1 / r2).

[0005] Specifically, as Figure 1As shown, the DC-DC converter is configured with a voltage dividing feedback network composed of two fixed sampling resistors r1 and r2. In order to realize software adjustment of the output voltage, a digital potentiometer RP is connected in series (or parallel, the purpose is the same, only the calculation formula is different) with r2. The digital potentiometer is actually an adjustable resistor whose resistance value can be adjusted by the host MCU. After the addition of RP in series, the expression of the output voltage becomes: Vout=Vref·(1+r1 / (r2+RP)), where Vref is the feedback reference voltage. Therefore, the MCU changes the resistance value of the digital potentiometer RP through GPIO signals or other communication methods to feedback the node voltage, thereby rewriting the output voltage Vout. Assuming that RP is divided into 64 grades between 0 and RP_max, the adjustment range of the output voltage is Vref* (1+r1 / (r2+RP_max))~Vref* (1+r1 / r2). Within this range, software can realize the adjustment of 64 voltage grades, i.e., obtain an equal number of discrete output voltages in the corresponding interval.

[0006] However, as can be seen from the expression of the output voltage above, since RP is in the denominator position, the output voltage Vout and the adjusted resistor RP exhibit a nonlinear relationship. Although software can realize the adjustment of 64 voltage grades, as RP gradually decreases, the interval of the output voltage adjustment will become increasingly sparse, i.e., leading to the inherent defect of "higher voltage section stepping denser, lower voltage section stepping sparser", which may not meet the required adjustment fineness. Taking the DC-DC power supply chip MP3910 (Vref=1.237 V) as an example, if r1=100 kΩ, the output voltage adjustment range is expected to be 3V~40V, then r2=r1 / (Vout_max / Vref-1)=100kΩ / (40V / 1.237V-1)=3.19kΩ, and r2=3kΩ. RP_max=R1 / (Vout_min / Vref-1)-r2=67.16kΩ, and RP_max=68kΩ. That is, a 64-grade digital potentiometer with a maximum resistance of 68kΩ is selected, and the adjustment range of the output voltage Vout is 2.98V~42.47V, which meets the requirements. During the RP adjustment process, the 64 output voltage grade curve is drawn as shown in Figure 2 .

[0007] It can be seen that when the RP resistance is large, the voltage intervals corresponding to each gear are dense, for example, the difference between the 64th gear voltage and the 63rd gear voltage is 0.026V, which is sufficient to meet the requirement of 0.1V for adjustment accuracy. However, when the RP is switched from 68kΩ to the low end (i.e., as the RP gradually decreases), the interval of the output voltage adjustment becomes sparse rapidly, the difference between the 1st gear voltage and the 2nd gear voltage is 6.31V, which is far lower than the requirement of 0.1V for low-end accuracy, and far fails to meet the requirement of voltage adjustment accuracy. If the number of gears of the digital potentiometer is simply increased, it cannot be realized in practical application; if additional digital potentiometers are used for coarse and fine adjustment or switching of different r1 and r2 for segmented adjustment, the hardware size, software algorithm and calibration complexity will be significantly increased, and the output will be out of the groove or overshoot during switching, which will affect the range of the output voltage. In other words, since the adjustable variable is directly placed at the denominator end of the feedback voltage division ratio, the resolution naturally deteriorates exponentially as the voltage decreases, so the prior art cannot simultaneously meet the requirements of voltage range selection and adjustment accuracy in the same topology.

[0008] In view of this, the present application is proposed. SUMMARY

[0009] The present application provides a power supply adjusting device and a voltage-adjustable power supply circuit, which can at least partially improve the above problems.

[0010] To achieve the above object, the present application adopts the following technical solutions: A voltage-adjustable power supply circuit, comprising: a DC-DC power supply circuit module, a sampling resistor assembly, and an analog level adjustable assembly, wherein the input end of the DC-DC power supply circuit module is used for connecting with an input voltage source, the output end of the DC-DC power supply circuit module is connected in series with the sampling resistor assembly, and the output end of the analog level adjustable assembly is electrically connected with the feedback end of the DC-DC power supply circuit module. The analog level adjustable assembly is configured to change the size of the output analog level to perform voltage feedback on the DC-DC power supply circuit module, so as to realize linear adjustment of the output voltage of the DC-DC power supply circuit module.

[0011] The present application also provides a power supply adjusting device, comprising the voltage-adjustable power supply circuit according to any one of the above.

[0012] In summary, the present application aims at the problem of resolution drop and fineness deficiency in low voltage section caused by nonlinearity of resistance-voltage in traditional digital potentiometer type DC-DC feedback network when wide range voltage regulation is performed, and proposes a voltage adjustable power supply circuit. The circuit adds sampling resistor R3 and operational amplifier unit on the basis of maintaining original R1 and R2 sampling voltage division network, injects adjustable analog level output by MCU into DC-DC feedback pin through operational amplifier gain, and makes output voltage and analog level present approximate linear relationship through voltage superposition method to 'pull bias' feedback node potential. By changing DAC level or PWM duty cycle, 64-grade or even higher resolution regulation with 0.1 V step and better than 1% accuracy can be obtained in 3 V~40 V full range, and grade interval is uniform, without increasing digital potentiometer or segment switching, with simple calculation, low hardware cost and convenient control. The circuit can be widely used in software controllable high precision power supply occasions such as thermal sensitive print head test fixture, ink amount control of ink jet head, motor torque regulation, and effectively solves the problem of difficult to balance regulation accuracy and range in prior art. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is a circuit block diagram of prior art power supply regulation scheme; Figure 2 is a 64 output voltage grade curve diagram of prior art power supply regulation scheme; Figure 3 is a circuit block diagram of voltage adjustable power supply circuit provided by the embodiment of the present application; Figure 4 is a schematic diagram of voltage adjustable power supply circuit of output DAC signal provided by the embodiment of the present application; Figure 5 is a schematic diagram of voltage adjustable power supply circuit of output PWM signal provided by the embodiment of the present application; Figure 6 is a 64 output voltage grade curve diagram of voltage adjustable power supply circuit provided by the embodiment of the present application. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical scheme and advantages of the present application clearer, further detailed description will be made to the present application combined with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0015] REFERENCE Figure 3As shown, the first embodiment of the present application discloses a voltage-adjustable power supply circuit, which comprises a DC-DC power supply circuit module, a sampling resistor assembly and an analog level adjustable assembly; an input end of the DC-DC power supply circuit module is used for being connected with an input voltage source; an output end of the DC-DC power supply circuit module is connected with the sampling resistor assembly in series; and an output end of the analog level adjustable assembly is electrically connected with a feedback end of the DC-DC power supply circuit module. The analog level adjustable assembly is configured to change the size of the output analog level to perform voltage feedback on the DC-DC power supply circuit module, so as to realize linear adjustment of the output voltage of the DC-DC power supply circuit module.

[0016] In the embodiment, preferably, the chip model of the DC-DC power supply circuit module can be MP3910. It can be understood that in other embodiments, other models of DC-DC power supply circuit modules can also be used, which are not limited here, but these schemes are within the protection scope of the present application.

[0017] In the embodiment, preferably, the sampling resistor assembly comprises a first sampling resistor and a second sampling resistor, wherein one end of the first sampling resistor is electrically connected with the output end of the DC-DC power supply circuit module, the other end of the first sampling resistor is electrically connected with one end of the second sampling resistor and the feedback end of the DC-DC power supply circuit module, and the other end of the second sampling resistor is grounded.

[0018] In the embodiment, preferably, the analog level adjustable assembly comprises a controller module, an operational amplifier module and a third sampling resistor, wherein the output end of the controller module is electrically connected with the input end of the operational amplifier module, and the output end of the operational amplifier module is electrically connected with the feedback end of the DC-DC power supply circuit module through the third sampling resistor; and the controller module is configured to output an analog level with adjustable size according to current demand, and the analog level is a DAC signal or a PWM signal output by the controller module.

[0019] In the embodiment, the injection of the analog level to the voltage feedback of the DC-DC power supply replaces the original potentiometer adjustment mode; the software can realize linear adjustment of the output voltage of the power supply by changing the high and low of the analog level, the range calculation of the voltage adjustment is simple, and the fine adjustment degree can easily meet the design requirements.

[0020] Specifically, the external input voltage source is connected to the input end of the DC-DC power supply circuit module, the power switch inside the module chops at a fixed frequency, and the energy is smoothed through the inductor, freewheeling diode and output capacitor to form an initial DC voltage Vout at the output end. One end of the first sampling resistor R1 is connected with Vout, and the other end is connected with the second sampling resistor R2 and the feedback pin FB of the DC-DC chip to form a node; the other end of R2 is directly grounded, thereby forming a traditional voltage dividing network, so that FB is stabilized near the chip reference voltage Vref without external intervention. At this time, if the analog level adjustable component remains silent, the circuit behaves as a common DC-DC converter, and the output voltage is uniquely determined by the R1, R2 ratio.

[0021] Preferably, the expression of the output voltage Vout of the DC-DC power supply circuit module is: Vout=R1* (Vref / R1+Vref / R2+Vref / R3-V*A / R3), wherein R1 is the first sampling resistor of the sampling resistor assembly, R2 is the second sampling resistor of the sampling resistor assembly, R3 is the third sampling resistor, Vref is the feedback reference voltage of the DC-DC power supply circuit module, V is the analog level output by the analog level adjustable component, and A is the operational amplifier gain of the operational amplifier module.

[0022] In the embodiment, when the input voltage Vin is converted by the DC-DC power supply circuit to obtain the output voltage Vout, assuming that the feedback reference voltage of the power supply circuit is Vref, and without considering the MCU control, the expression of the output voltage is: Vout=Vref*(1+R1 / R2). The MCU outputs an adjustable analog level, which is amplified by the operational amplifier and then connected to the feedback pin of the DC-DC power supply through the sampling resistor R3. The analog level can be obtained directly by using the DAC output of the MCU, or by filtering the PWM signal. Assuming that the level value is V, and the gain of the operational amplifier is set to A, then a voltage of V*A will be injected into the feedback voltage of the DC-DC power supply through the sampling resistor R3. Through the superposition principle in the circuit, it is easy to calculate that the expression of the output voltage becomes: Vout=R1*(Vref / R1+Vref / R2+Vref / R3-V*A / R3).

[0023] Specifically, when the output voltage needs to be changed, the controller module first obtains a target voltage value according to the host computer or an internal algorithm, and converts it into a corresponding DAC code value or PWM duty cycle, and then presents an analog level of 0V to full amplitude at the output end of the controller module (i.e. the software can adjust the output voltage by changing the value of the analog level V (adjusting the output of the DAC or adjusting the duty cycle of the PWM signal)). The analog level is sent to the non-inverting input terminal of the operational amplifier module, and the operational amplifier module is buffered with a unit gain or a set gain, and then injected into the FB node through the third sampling resistor R3. Since the output impedance of the operational amplifier is very low, the injection current size only depends on the difference between R3 resistance value and the output voltage of the operational amplifier, so the FB node voltage is linearly raised or lowered; after the DC-DC chip senses the offset, it automatically adjusts the duty cycle to make the FB return to Vref, and the result is that the output voltage Vout changes approximately linearly with the analog level. The whole process does not need to switch any mechanical or digital variable elements, so there is no overshoot or discontinuity caused by gear jumping, and the output voltage can be continuously, uniformly and finely adjusted in the range of 3V to 40V, and the interval between adjacent step voltages remains constant, which significantly improves the repeatability of the test fixture in the resistance correction of the thermal print head.

[0024] Further, the range and fineness of voltage adjustment are calculated. When the voltage V is adjusted to 0, the output voltage is maximum Vout_max=R1*(Vref / R1+Vref / R2+Vref / R3); when the voltage V is adjusted to the maximum value V_max, the output voltage is minimum Vout_min=R1*(Vref / R1+Vref / R2+Vref / R3-V_max*A / R3). Similarly, using the DC-DC power chip MP3910 as an example for calculation, its Vref=1.237V, R1=100kΩ, R2=10kΩ, and the adjustment range of the output voltage is expected to be 3V~40V, then Vout_max=40V, and substituting the above maximum output voltage formula can obtain R3=Vref / (Vout_max / R1-Vref / R1-Vref / R2)=1.237V / (40V / 100kΩ-1.237V / 100kΩ-1.237V / 10kΩ)=4.497kΩ, and R3=4.2kΩ is taken.

[0025] The minimum voltage calculation formula is substituted by Vout_min=3V, R1, R2, R3, and Vref, and V_max*A=R3*(Vref / R1+Vref / R2+Vref / R3-Vout_min / R1)=1.68V can be obtained. Considering that the maximum value of the analog level V adjustment is usually V_max=3.3V, the gain of the operational amplifier is set to A=1.68V / 3.3V=0.509, and A=0.51 is taken. After the above parameter setting, that is, Vref=1.237V, R1=100kΩ, R2=10kΩ, R3=4.2kΩ, V_max=3.3V, and A=0.51, the adjustment range of the output voltage Vout is 2.99V~43.06V, which meets the requirement. Assuming that the adjustment gear of the software for the analog level V is still 64 gears, 64 output voltage gear curves are shown in Figure 6 during the adjustment of the voltage V. The output voltage realizes the adjustment of 64 gears in the range of 2.99V~43.06V, and the voltage interval between the gears becomes uniform, which is 0.626V, and completely meets the requirement that the voltage adjustment precision needs to reach 0.1V.

[0026] In the above embodiment, the analog level can be a DAC signal or a PWM signal, which can be generated by the following method: Please refer to Figure 4 In an embodiment, the controller module includes an MCU, a feedback resistor, and an input resistor. The output end of the MCU is electrically connected to one end of the input resistor and outputs a DAC signal. The other end of the input resistor is electrically connected to the positive electrode of the operational amplifier module. One end of the feedback resistor is electrically connected to the negative electrode of the operational amplifier module. The other end of the feedback resistor is electrically connected to the output end of the operational amplifier module.

[0027] The expression of the operational amplifier gain A is A=1+Rf / Rin, wherein Rf is the feedback resistor, and Rin is the input resistor.

[0028] Specifically, in the embodiment, the MCU inside the controller module converts the target voltage value into an analog signal of 0~Vref_mcu after power-on through internal DAC, the signal is sent to the non-inverting terminal of the operational amplifier module through input resistance Rin, amplified, and connected to R3 before being injected into the feedback pin of the power supply chip; the feedback resistance Rf of the operational amplifier module is connected between the output terminal and the inverting terminal, forming a non-inverting amplification structure, and its gain A=1+Rf / Rin. Since the full-scale output voltage of the MCU is usually higher than the required injection voltage of the feedback pin of the DC-DC chip, by reasonably selecting the ratio of Rf and Rin, the DAC range can be compressed to the optimal injection interval, avoiding signal saturation and retaining sufficient adjustment margin; at the same time, the low output impedance of the operational amplifier module makes the injection current size only limited by the third sampling resistance R3, the FB node voltage rises and falls linearly with the DAC code value, and the output voltage Vout also changes uniformly in steps, fundamentally eliminating the low-voltage segment step sparsity problem caused by the traditional "resistance in the denominator".

[0029] Please refer to Figure 5 In one embodiment, the controller module comprises an MCU, a filter resistor, a filter capacitor, a feedback resistor, and an input resistor, the output terminal of the MCU is electrically connected with one end of the filter resistor and outputs a PWM signal, the other end of the filter resistor is electrically connected with one end of the input resistor and one end of the filter capacitor, the other end of the filter capacitor is grounded, the other end of the input resistor is electrically connected with the positive electrode of the operational amplifier module, one end of the feedback resistor is electrically connected with the negative electrode of the operational amplifier module, and the other end of the feedback resistor is electrically connected with the output terminal of the operational amplifier module.

[0030] Specifically, in the present embodiment, the MCU inside the controller module calculates the PWM duty cycle corresponding to the target voltage according to the host computer instructions, and outputs a square wave with a preset frequency in Hz at its PWM pin; the square wave is connected to a low-pass network composed of a filtering capacitor through a filtering resistor, and is subjected to filtering processing, with the other end of the filtering capacitor grounded, so as to smooth the square wave into a DC analog level with a ripple lower than a preset value. The smoothed signal is sent to the non-inverting terminal of the operational amplifier module through an input resistor, and a feedback resistor is connected across the output of the operational amplifier and the inverting terminal, forming a non-inverting amplification structure, the gain of which is accurately set by the ratio of the feedback resistor to the input resistor. Since the PWM duty cycle can be fine-tuned in single-cycle steps between 0% and 100%, the equivalent resolution of the DAC is only limited by the number of bits of the MCU timer, and theoretically 1024 levels or even higher voltage steps can be obtained; and the low output impedance of the operational amplifier module ensures that the injected current size is only limited by the third sampling resistor, the FB node voltage linearly rises and falls with the PWM duty cycle, and the output voltage Vout also changes uniformly in steps, fundamentally eliminating the problem of sparse steps in the low-voltage section caused by the traditional "resistor in the denominator". In short, after the PWM signal is filtered through R4 and C4, an analog level can be obtained, and the adjustment of the level value is realized by changing the duty cycle of the PWM signal.

[0031] In summary, by replacing the "variable feedback resistor adjustment method" in the feedback network with the "injectable analog level adjustment method", the feedback voltage perceived by the DC-DC chip changes linearly with the DAC or PWM signal output by the MCU, so that the output voltage is uniformly adjusted in the range of 3 V to 40 V, avoiding the problems of sparse low-end steps and high-end jump overruns caused by the nonlinearity of the traditional digital potentiometer scheme.

[0032] The implementation mode only connects a fixed resistor R3 in series at the original R1, R2 voltage division node, and injects the analog level buffered by the operational amplifier into the node (i.e. after the analog level output, the operational amplifier gain amplification is further entered into the feedback pin of the DC-DC power supply chip), on the one hand, the output capacity of the analog level is increased, on the other hand, the adjustment range and the slope of the output voltage are facilitated to adjust. Without changing the power stage and compensation network, one ordinary operational amplifier and three SMD resistors are added in hardware, the defects of the original circuit scheme are solved from the root, the digital potentiometer and its interface isolation device are saved, the BOM cost and the PCB area are reduced; only the DAC code or the PWM duty cycle needs to be changed monotonically on the software side, and the output voltage with approximate equal steps can be obtained, the algorithm development and the calibration process are simplified, and the implementation is easy; the injection path impedance is high and limited by R3, the MCU pin can be protected when the feedback pin is accidentally short-circuited, and the reliability in the production line application is improved; the whole circuit keeps the original loop characteristics of the DC-DC chip, the load regulation and the temperature drift are determined by the fixed resistance ratio, the full-scale accuracy is better than 1%, the adjustment fineness reaches 0.1 V, and the device can be directly used in the occasions requiring software controllable high-precision power supply, such as thermal sensitive print head test fixture, ink amount control of inkjet head, motor torque driving and the like, and the needs of wide range, high resolution, low cost and easy production are considered.

[0033] The second embodiment of the present application provides a power supply adjusting device including the voltage-adjustable power supply circuit according to any one of the above.

[0034] The above is the preferred embodiment of the present application, and it should be pointed out that, for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements are also considered to be within the protection scope of the present application.

Claims

1. A voltage-adjustable power supply circuit, characterized in that, include: The DC-DC power supply circuit module comprises a sampling resistor assembly and an analog level adjustable assembly. The input terminal of the DC-DC power supply circuit module is connected to an input voltage source, the output terminal of the DC-DC power supply circuit module is connected in series with the sampling resistor assembly, and the output terminal of the analog level adjustable assembly is electrically connected to the feedback terminal of the DC-DC power supply circuit module. The analog level adjustable component is configured to provide voltage feedback to the DC-DC power supply circuit module by changing the magnitude of the output analog level, so as to achieve linear adjustment of the output voltage of the DC-DC power supply circuit module.

2. The voltage-adjustable power supply circuit according to claim 1, characterized in that, The chip model of the DC-DC power supply circuit module is MP3910.

3. The voltage-adjustable power supply circuit according to claim 1, characterized in that, The sampling resistor assembly includes a first sampling resistor and a second sampling resistor. One end of the first sampling resistor is electrically connected to the output terminal of the DC-DC power supply circuit module, and the other end of the first sampling resistor is electrically connected to one end of the second sampling resistor and the feedback terminal of the DC-DC power supply circuit module. The other end of the second sampling resistor is grounded.

4. The voltage-adjustable power supply circuit according to claim 1, characterized in that, The analog level adjustable component includes a controller module, an operational amplifier module, and a third sampling resistor. The output terminal of the controller module is electrically connected to the input terminal of the operational amplifier module, and the output terminal of the operational amplifier module is electrically connected to the feedback terminal of the DC-DC power supply circuit module through the third sampling resistor. The controller module is configured to output an adjustable analog level according to current needs. The analog level is a DAC signal or a PWM signal output by the controller module.

5. The voltage-adjustable power supply circuit according to claim 4, characterized in that, The expression for the output voltage Vout of the DC-DC power supply circuit module is: Vout = R1 * (Vref / R1 + Vref / R2 + Vref / R3 - V * A / R3), where R1 is the first sampling resistor of the sampling resistor assembly, R2 is the second sampling resistor of the sampling resistor assembly, R3 is the third sampling resistor, Vref is the feedback reference voltage of the DC-DC power supply circuit module, V is the analog level output by the analog level adjustable component, and A is the operational amplifier gain of the operational amplifier module.

6. The voltage-adjustable power supply circuit according to claim 5, characterized in that, The controller module includes an MCU, a feedback resistor, and an input resistor. The output terminal of the MCU is electrically connected to one end of the input resistor and outputs a DAC signal. The other end of the input resistor is electrically connected to the positive terminal of the operational amplifier module. One end of the feedback resistor is electrically connected to the negative terminal of the operational amplifier module, and the other end of the feedback resistor is electrically connected to the output terminal of the operational amplifier module.

7. The voltage-adjustable power supply circuit according to claim 6, characterized in that, The expression for the op-amp gain A is A = 1 + Rf / Rin, where Rf is the feedback resistor and Rin is the input resistor.

8. The voltage-adjustable power supply circuit according to claim 4, characterized in that, The controller module includes an MCU, a filter resistor, a filter capacitor, a feedback resistor, and an input resistor. The output terminal of the MCU is electrically connected to one end of the filter resistor and outputs a PWM signal. The other end of the filter resistor is electrically connected to one end of the input resistor and one end of the filter capacitor. The other end of the filter capacitor is grounded. The other end of the input resistor is electrically connected to the positive terminal of the operational amplifier module. One end of the feedback resistor is electrically connected to the negative terminal of the operational amplifier module, and the other end of the feedback resistor is electrically connected to the output terminal of the operational amplifier module.

9. A power regulation device, characterized in that, Includes a voltage-adjustable power supply circuit as described in any one of claims 1 to 8.

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