Voltage-adjustable DC power supply circuit and voltage dynamic calibration method

Abstract

The invention discloses a voltage-adjustable direct current power supply circuit and a voltage dynamic calibration method, and relates to the technical field of printers, the voltage-adjustable direct current power supply circuit comprises a power supply input and protection module, a voltage adjusting module, an interface and signal adjusting module and a voltage dividing module, the control module is used for controlling connection and disconnection of a power supply and performing on-off control of the power supply; the voltage regulation module provides stable voltage output and adapts to different voltage requirements by regulating internal parameters of the module; the interface and signal adjusting module processes and adjusts signals through a chip U26, is used for communicating with external equipment, and is connected to different signals to perform data transmission and control with the external equipment; the voltage dividing module is used for generating stable reference voltage and providing the stable reference voltage to the ADC module for accurate analog-to-digital conversion; through cooperative work of the modules, accurate control and adjustment of voltage output are realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of printers, and particularly relates to a direct-current power supply circuit capable of adjusting voltage and a voltage dynamic calibration method. BACKGROUND

[0002] At present, most of the DC direct-current power supplies are designed to mainly output set voltage, and if the voltage output value needs to be adjusted, the voltage dividing resistor needs to be adjusted. This design mode has a big defect, that is, when different loads or use environments change, the resistor value needs to be constantly adjusted, and this condition sample needs to be returned to the factory for processing, which leads to poor flexibility, high maintenance cost and impedance matching problems. SUMMARY

[0003] The present application is provided to solve the above technical problems, and provides a direct-current power supply circuit capable of adjusting voltage and a voltage dynamic calibration method.

[0004] In one aspect, the technical scheme of the present application is implemented as follows:

[0005] A direct-current power supply circuit capable of adjusting voltage comprises a power input and protection module, a voltage regulation module, an interface and signal regulation module and a voltage dividing module.

[0006] The power input and protection module is responsible for inputting, preliminarily filtering and overcurrent protection of the power supply, is used for controlling the on and off of the power supply, and performs switching control of the power supply.

[0007] The voltage regulation module provides stable voltage output, and adjusts internal parameters of the module to adapt to different voltage requirements.

[0008] The interface and signal regulation module processes and adjusts signals through a chip U26, is used for communicating with external devices, and performs data transmission and control with the external devices through connection to different signals.

[0009] The voltage dividing module is used for generating a stable reference voltage, providing the reference voltage to an ADC module, and performing accurate analog-digital conversion.

[0010] Further, the power input and protection module comprises a fuse F5, one end of the fuse F5 is connected with the ground through a capacitor C129, the capacitor C129 is also connected with VDD INKJET1, the other end of the fuse F5 is connected with the ground through a capacitor C130, the capacitor C130 is also connected with the ground through a capacitor C131, the capacitor C131 is also connected with the junction of the collector of a transistor Q6, a resistor R156 and one end of a capacitor C932, the other end of the resistor R156 and the capacitor C932 is connected with the ground respectively, the emitter of the transistor Q6 is connected with the ground, the base of the transistor Q6 is connected with the junction of a resistor R154, a resistor R155 and one end of a resistor R157, the other end of the resistor R157 is connected with the ground, the other end of the resistor R154 is connected with VCC 3V3M, the other end of the resistor R155 is connected with M1 EN PVCOM.

[0011] Further, the voltage regulation module comprises a chip U25, the first pin of the chip U25 is connected with the eighth pin of the chip U25 through a capacitor C128, the second pin of the chip U25 is also connected with a resistor R149, the third pin of the chip U25 is connected with one end of a capacitor C932, the fourth pin of the chip U25 is connected with the ground through a resistor R150, the seventh pin and the ninth pin of the chip U25 are connected with the ground respectively, the fifth pin of the chip U25 is connected with the junction of a resistor R158 and one end of a resistor R152, the sixth pin of the chip U25 is connected with the junction of a capacitor C137 and one end of a resistor R151, the other end of the resistor R151 is also connected with the ground through a capacitor C138, the other end of the capacitor C137 is connected with the ground, the eighth pin of the chip U25 is also connected with the junction of a diode D45 and one end of an inductor L9, the other end of the diode D45 is connected with the ground.

[0012] Further, the interface and signal regulation module comprises a chip U26, the first pin of the chip U26 is connected with the other end of a resistor R158, the second pin of the chip U26 is connected with the junction of a capacitor C140, a capacitor C141 and VDD DP 3V3, the capacitor C140 and the capacitor C141 are also connected with the ground respectively, the third pin of the chip U26 is connected with the ground, the fourth pin of the chip U26 is connected with M1 DP SCK through a resistor R161, the fifth pin of the chip U26 is connected with M1 DP DATA through a resistor R162, the sixth pin of the chip U26 is connected with the junction of a resistor R159 and M1 DPVCOM CS through a resistor R160, the resistor R159 is also connected with VCC 3V3M, the eighth pin of the chip U26 is connected with the ground.

[0013] Further, the voltage dividing module comprises an inductor L9, one end of the inductor L9 is connected at the junction of one end of a capacitor C132 and the other end of a resistor R152, the other end of the capacitor C132 is further connected with the ground, the other end of the capacitor C132 is further connected with the ground through a capacitor C133, the capacitor C133 is further connected with the ground through a capacitor C134, the capacitor C134 is further connected at the junction of one end of a capacitor C135 and VCC_M1_VCCM, the other end of the capacitor C135 is further connected with the ground, one end of the capacitor C135 is further connected with an LED through a resistor R147, the LED is further connected with the ground, the resistor R147 is further connected at the junction of a resistor R148 and one end of a capacitor C136, the other end of the capacitor C136 is connected with the ground, the other end of the resistor R148 is further connected at the junction of a resistor R153, a capacitor C139 and M1_ADC_VCOM, the resistor R153 and the capacitor C139 are further connected with the ground respectively.

[0014] Further, the fuse F5 is a 2A self-recovery fuse, the capacitor C130 and the capacitor C131 are filter circuits for filtering the power input of VDD_INKJET1; the resistor R149 and the resistor R156 constitute a voltage dividing circuit input PIN3 of U25, for setting the starting voltage, the capacitor C932 plays a role of stabilizing voltage; the resistor R154, the resistor R157, the resistor R155 and the transistor Q6 constitute an EN switch circuit of U25; the capacitor C128 is a bootstrap capacitor, the capacitor C168 is a soft start capacitor; the resistor R150 sets the output PWM frequency; the diode D45 is a Schottky diode; the resistor R158, the resistor R152 and the chip U26 constitute a negative feedback network, the output level is divided and then input PIN5 of the chip U25 and the reference level are compared; the resistor R151, the capacitor C137 and the capacitor C138 set the response bandwidth of the internal comparator signal; the chip U26 is a digital potentiometer: AD5160BRJZ10-RL7; VDD_DP_3V3 is the power supply of U26; wherein M1_DP_SCK, M1_DPVCOM_CS and M1_DP_DATA are the clock chip selection and data line of the digital potentiometer.

[0015] On the other hand, the application further comprises a voltage dynamic calibration method applied to an adjustable voltage DC power supply circuit, comprising the following steps:

[0016] In each power-on initialization, the control unit reads the data of the sensor; the correction amount required by the reference voltage is calculated according to the preset model;

[0017] The correction amount is written into the adjustable resistance unit through the digital interface to update the reference value;

[0018] A low-pass link is added in the sensing path to filter high-frequency thermal disturbance, the abstract model is discretized into a data curve and solidified into a non-volatile storage unit, after the non-linear curve is segmented and solidified, a digital compensation value is converted into an analog fine adjustment amount through double interpolation fusion-high resolution DAC link, and the fine adjustment amount is injected into a feedback loop to realize real-time closed-loop correction of the reference voltage.

[0019] The utility model has the advantages of:

[0020] By introducing an integrated adjustable voltage DC power supply circuit, the problem of poor flexibility, high maintenance cost and impedance matching in traditional printer power supply design is effectively solved. The circuit is composed of power input and protection module, voltage regulation module, interface and signal regulation module, and voltage dividing module. Through the cooperative work of these modules, accurate control and regulation of voltage output are realized.

[0021] Firstly, the power input and protection module ensures stable input and overcurrent protection of the power supply through self-restoring fuse and filter capacitor. The voltage regulation module uses chip U25 to provide stable voltage output through internal parameter adjustment to adapt to different voltage requirements. The interface and signal regulation module uses digital potentiometer U26 to communicate with external devices through SPI interface to realize software regulation of voltage output, thereby eliminating the need for physical adjustment of the voltage dividing resistor, greatly reducing maintenance cost and improving flexibility. The voltage dividing module provides stable reference voltage for the ADC module to ensure the accuracy of analog-to-digital conversion. This design allows the printer to dynamically adjust the voltage output according to different loads and use environments, optimizing the printing effect and reducing performance degradation caused by impedance matching problems.

[0022] This method upgrades the traditional calibration mode which relies on manual, mechanical and open-loop to electronic non-contact, automatic real-time and closed-loop continuous dynamic calibration mode through the whole closed-loop idea of power-on sampling, model calculation, digital writing, disturbance filtering, curve solidification, interpolation fusion and fine adjustment injection. The reference value is no longer affected by device aging, environmental fluctuations and mechanical wear, and the long-term stability is changed from passive tolerance to active offset. The low-pass link and solidified curve jointly suppress external disturbance and internal noise, significantly improving the purity of power output. Double interpolation fusion considers smoothness and fidelity, high-resolution DAC realizes delicate stepless correction, feedback loop continuously locks target voltage, and the system always runs at the best working point. The calibration process of the present application has zero manual intervention, and the maintenance cost is greatly reduced. There is no mechanical adjustable part, and the reliability, service life and shock resistance are simultaneously enhanced. The environmental adaptability is expanded, and the output quality can be maintained consistent in wide temperature, high humidity and strong vibration environments. The closed-loop correction is performed in real time, eliminating cumulative drift, and the long-term precision of the power supply no longer deteriorates with time. The overall scheme has small hardware increment and reusable software, providing a simple, efficient and sustainable voltage precision protection method for precision instruments, high-end equipment and unattended systems. BRIEF DESCRIPTION OF DRAWINGS

[0023] Fig. 1 is a structural schematic diagram of the present application;

[0024] Fig. 2 is a circuit schematic diagram of the present application. DETAILED DESCRIPTION

[0025] To further illustrate the technical means and effects taken by the present application to achieve the predetermined inventive purpose, the specific embodiments of the present application are described below to facilitate the understanding of the present application by those skilled in the art. However, it should be clear that the present application is not limited to the scope of the specific embodiments. For those skilled in the art, it is obvious that any changes within the spirit and scope of the present application as defined and determined by the appended claims are obvious, and all the inventions utilizing the concept of the present application are within the scope of protection.

[0026] Example 1

[0027] As shown in Figs. 1-2 , the adjustable voltage DC power supply circuit of the present application comprises

[0028] a power input and protection module responsible for the input, preliminary filtering and overcurrent protection of the power supply, used to control the on and off of the power supply, realizing the switching control of the power supply;

[0029] a voltage regulation module providing stable voltage output, adapting to different voltage requirements by adjusting the internal parameters of the module;

[0030] an interface and signal regulation module processing and adjusting signals through chip U26, used for communication with external devices, and transmitting and controlling data with external devices through connection to different signals;

[0031] a voltage division module for generating a stable reference voltage, provided to the ADC module through M1_ADC_VCOM for accurate analog-digital conversion.

[0032] Further, the power input and protection module comprises a fuse F5, one end of the fuse F5 is connected with the ground through a capacitor C129, the capacitor C129 is also connected with VDD INKJET1, the other end of the fuse F5 is connected with the ground through a capacitor C130, the capacitor C130 is also connected with the ground through a capacitor C131, the capacitor C131 is also connected with the junction of the collector of a transistor Q6, a resistor R156 and one end of a capacitor C932, the other end of the resistor R156 and the capacitor C932 is connected with the ground respectively, the emitter of the transistor Q6 is connected with the ground, the base of the transistor Q6 is connected with the junction of a resistor R154, a resistor R155 and one end of a resistor R157, the other end of the resistor R157 is connected with the ground, the other end of the resistor R154 is connected with VCC 3V3M, the other end of the resistor R155 is connected with M1 EN PVCOM.

[0033] Further, the voltage regulation module comprises a chip U25, the first pin of the chip U25 is connected with the eighth pin of the chip U25 through a capacitor C128, the second pin of the chip U25 is also connected with a resistor R149, the third pin of the chip U25 is connected with one end of a capacitor C932, the fourth pin of the chip U25 is connected with the ground through a resistor R150, the seventh pin and the ninth pin of the chip U25 are connected with the ground respectively, the fifth pin of the chip U25 is connected with the junction of a resistor R158 and one end of a resistor R152, the sixth pin of the chip U25 is connected with the junction of a capacitor C137 and one end of a resistor R151, the other end of the resistor R151 is also connected with the ground through a capacitor C138, the other end of the capacitor C137 is connected with the ground, the eighth pin of the chip U25 is also connected with the junction of a diode D45 and one end of an inductor L9, the other end of the diode D45 is connected with the ground.

[0034] Further, the interface and signal regulation module comprises a chip U26, the first pin of the chip U26 is connected with the other end of a resistor R158, the second pin of the chip U26 is connected with the junction of a capacitor C140, a capacitor C141 and VDD DP 3V3, the capacitor C140 and the capacitor C141 are also connected with the ground respectively, the third pin of the chip U26 is connected with the ground, the fourth pin of the chip U26 is connected with M1 DP SCK through a resistor R161, the fifth pin of the chip U26 is connected with M1 DP DATA through a resistor R162, the sixth pin of the chip U26 is connected with the junction of a resistor R159 and M1 DPVCOM CS through a resistor R160, the resistor R159 is also connected with VCC 3V3M, the eighth pin of the chip U26 is connected with the ground.

[0035] Further, the voltage dividing module comprises an inductor L9, one end of the inductor L9 is connected at the junction of one end of a capacitor C132 and the other end of a resistor R152, the other end of the capacitor C132 is further connected with the ground, the other end of the capacitor C132 is further connected with the ground through a capacitor C133, the capacitor C133 is further connected with the ground through a capacitor C134, the capacitor C134 is further connected at the junction of one end of a capacitor C135 and VCC_M1_VCCM, the other end of the capacitor C135 is further connected with the ground, one end of the capacitor C135 is further connected with an LED through a resistor R147, the LED is further connected with the ground, the resistor R147 is further connected at the junction of a resistor R148 and one end of a capacitor C136, the other end of the capacitor C136 is connected with the ground, the other end of the resistor R148 is further connected at the junction of a resistor R153, a capacitor C139 and M1_ADC_VCOM, the resistor R153 and the capacitor C139 are further connected with the ground respectively.

[0036] Further, the fuse F5 is a 2A self-recovery fuse, which is automatically disconnected when the input current exceeds 2A; the capacitor C130 and the capacitor C131 are filter circuits for filtering the VDD_INKJET1 power input; the resistor R149 and the resistor R156 form a voltage divider circuit input PIN3 of U25, set the starting voltage, the capacitor C932 plays a role in stabilizing the voltage, preventing the circuit from being disturbed to cause false triggering protection, and enhancing the reliability of the circuit; the resistor R154, the resistor R157, the resistor R155 and the transistor Q6 form the EN switch circuit of U25, when the system has not run, VCC_3V3M controls the EN control signal to low level, keeping U25 closed state, no voltage output; after the system runs, the output M1_EN_PVCOM is low, at this time the EN signal is opened, the voltage division level VEN=VDD_INKJET1*(R156 / (R149+R156)); the capacitor C128 is a bootstrap capacitor, and the capacitor C168 is a soft start capacitor; the resistor R150 sets the output PWM frequency; the diode D45 is a Schottky diode, which helps the L9 inductor to continue to flow; the resistor R158, the resistor R152 and the chip U26 form a negative feedback network, which compares the output voltage after voltage division with the reference voltage; the resistor R151, the capacitor C137 and the capacitor C138 set the response bandwidth of the internal comparator signal; the chip U26 is a digital potentiometer: AD5160BRJZ10-RL7; VDD_DP_3V3 is the power supply of U26, which can adjust the resistance value of the digital potentiometer at any time through the SPI interface, so that the output voltage value VCC_M1_VCOM can be changed according to the demand; wherein M1_DP_SCKM1_DPVCOM_CSM1_DP_DATA is the clock chip selection and data line of the digital potentiometer, and the software can adjust the resistance output of the digital potentiometer through the SPI communication protocol; the digital potentiometer is 8-bit, so the software adjustment accuracy: the range of each gear is (30.028-17.152) / 256=0.05029V; when R152=402K and R158=11.5K, the output range of the circuit is 17.152V-30.028V.

[0037] Working principle:

[0038] High voltage VDD_INKJET1 filtered input U25 PIN2 foot, PIN3 EN foot detects the input level in the range, will start the internal MOS through L9 inductance to C132 C133 C134 capacitor to a specific frequency of PWM charging, when the capacitor to set the voltage, U53 PIN5 detects the feedback signal is higher than the reference level after the internal MOS is closed, D25 diode conduction for L16 inductance freewheeling, output voltage setting: Uout = ref * (R152 + R158 + RU26) / (R158 + RU26); RU26 is the output resistance value of U26 digital potentiometer setting; When the load consumes the capacitor, U53 PIN5 detects the feedback signal is lower than the reference level after the internal MOS is started again to charge, so the cycle, to achieve the effect of dynamic voltage regulation. The circuit design can adjust the DC voltage VCC_M1_VCOM output value in real time according to the load demand, as long as it is within the range, it can be applied; If a larger low voltage range is required, then adjust the resistance value of R152 R158 according to the actual demand, so you can change the voltage output range.

[0039] The present application is mainly used for digital inkjet printer, for outputting different voltage to control different print effect of inkjet. Through the cooperative work of power input and protection module, voltage regulation module, interface and signal adjustment module and voltage division module, the accurate voltage control of different inkjet in digital inkjet printer is realized to adapt to different print effect demand. The circuit can dynamically adjust the output voltage VCC_M1_VCOM according to the load demand, and the output range can be adjusted between 17.152V and 30.028V. Through the SPI interface of digital potentiometer U26, the software can change the output voltage value in real time, and the adjustment accuracy of each gear is 0.05029V, so as to provide flexible and accurate voltage output for inkjet printer and optimize the print quality. In addition, the circuit design also includes self-restoring fuse and filter circuit, which enhances the safety and stability of the circuit.

[0040] Embodiment 2

[0041] In this embodiment, a voltage dynamic calibration method is applied to a DC power supply circuit with adjustable voltage:

[0042] In each power-on initialization, the control unit reads the temperature sensor data;

[0043] Compensate the reference voltage according to the temperature-voltage offset curve;

[0044] Write the compensated resistance value to the digital potentiometer U26 through the SPI interface;

[0045] An RC low-pass filter with time constant τ = 100 ms is connected in series to the temperature sensor output to suppress the transient thermal noise of the printhead.

[0046] The temperature-voltage offset curve is discretized into 64 piecewise lines and stored in the MCU EEPROM.

[0047] Linear interpolation and cubic spline interpolation are used between the nodes of the piecewise line to calculate the compensation value, and the average of the two is taken as the compensation value, so that the temperature error is < ±0.1 °C and the converted voltage is < ±5 mV.

[0048] The compensation value is converted into a 0-1 V fine-tuning voltage by a 16-bit Σ-Δ DAC and superimposed on the U25 feedback node to achieve closed-loop calibration.

[0049] The core of voltage dynamic calibration is to monitor temperature changes in real time and compensate for output voltage in a closed loop to ensure that the printhead can obtain accurate working voltage (VCC_M1_VCOM) under different environmental temperatures. The implementation steps are as follows:

[0050] Power-on initialization and temperature data acquisition

[0051] A high-precision temperature sensor (such as an NTC thermistor or a digital temperature chip DS18B20) is integrated into the circuit and installed near the heat source area of the printhead (temperature response time ≤100 ms) to sense the working temperature of the printhead in real time.

[0052] Each time the printer is powered on, the control unit (MCU) first reads the initial data of the temperature sensor (denoted as T0) through the I²C or ADC interface and triggers the calibration program. At this time, the digital potentiometer U26 (AD5160BRJZ10-RL7) is reset to the default resistance value (middle position, corresponding to an output voltage of 23.59V), providing a reference for subsequent calibration.

[0053] The discretization and storage of the temperature-voltage offset curve, temperature changes will cause the parameters of resistors, capacitors and other components in the circuit to drift (such as the temperature coefficient of the reference voltage source of the U25 chip is ±10ppm / ℃), eventually resulting in output voltage offset. The curve changes nonlinearly in the range of -10℃~60℃ (the offset increases rapidly in the low temperature zone, and tends to be flat in the high temperature zone), in order to facilitate MCU calculation, the curve is discretized into 64 piecewise lines, each corresponding to a temperature interval of 0.5℃ (total coverage -10℃~60℃, a temperature difference of 70℃, 64 pieces can meet the accuracy requirements). The piecewise line node data (such as T=-10℃ offset -32mV, T=25℃ offset 0mV, T=60℃ offset +45mV) is stored in the EEPROM of the MCU and will not be lost after power-off.

[0054] For the filtering of temperature signals, when the print head is working, the process of nozzle vibration, ink ejection, etc. can produce instantaneous thermal noise (frequency range 10kHz~1MHz), resulting in fluctuations in the output signal of the temperature sensor (the maximum fluctuation amplitude can reach ±0.5℃), which will introduce errors if directly used for calibration. RC low-pass filter: a RC low-pass filter (resistor R=10kΩ, capacitor C=10µF, time constant τ=R×C=100ms) is connected in series at the output end of the temperature sensor, which can effectively filter out high-frequency noise, reduce the amplitude of temperature signal fluctuations to ±0.05℃, and meet the accuracy requirements of calibration.

[0055] Interpolation calculation of compensation value: interpolation requirement: the actual temperature may be between two nodes of the broken line (such as 25.3℃ between 25℃ and 25.5℃), and the compensation value needs to be calculated by interpolation.

[0056] Double algorithm parallel, linear interpolation: based on the offset of the adjacent two nodes, the compensation value of the intermediate temperature is calculated in proportion (fast calculation speed, error ≤±0.1mV).

[0057] Cubic spline interpolation: through polynomial fitting curve trend, the error of nonlinear region is reduced (higher accuracy, error ≤±0.05mV).

[0058] Take the average of the two interpolation results as the final compensation value, taking into account the calculation efficiency and accuracy, to ensure that when the temperature error is <±0.1℃, the converted voltage error is <±5mV.

[0059] DAC conversion of compensation value and closed-loop calibration: the role of 16-bit Σ-Δ DAC in the present application, the compensation value (voltage fine tuning amount) needs to be converted into an analog signal before being superimposed into the feedback loop. Select a 16-bit Σ-Δ DAC (such as AD7792), whose resolution can reach 1V / 65536≈15.26µV, ensuring fine tuning accuracy.

[0060] The closed-loop control process converts the compensation value into a fine-tuning voltage (Vtrim) of 0-1V by the DAC, and the Vtrim is superimposed on the feedback node (PIN5) of the U25 chip to form a new feedback signal (Vfb'=Vfb+Vtrim) after being superimposed with the original feedback voltage (Vfb). The U25 adjusts the PWM duty cycle according to the difference between Vfb' and the internal reference voltage (Vref=2.5V), and finally stabilizes the output voltage VCC_M1_VCOM at the target value (error≤±5mV). SPI communication adjustment: the MCU writes the compensated resistance value into the digital potentiometer U26 through the SPI interface (M1_DP_SCK clock line, M1_DP_DATA data line), and adjusts the voltage division ratio of the negative feedback network in real time to realize dynamic calibration.

[0061] The dynamic calibration program is executed every 10ms (synchronized with the working period of the printer nozzle), ensuring that the voltage offset can be compensated in time when the temperature changes rapidly (such as when the printer works continuously for 30 minutes and the nozzle temperature rises from 25℃ to 50℃). Through oscilloscope monitoring, the dynamic fluctuation amplitude of the output voltage can be controlled within ±3mV, which is much better than the ±50mV of traditional power supplies.

[0062] In the embodiment, through the four-step self-loop of sensing, modeling, interpolation and injection, the purpose of quickly adjusting the voltage is achieved. In the embodiment, at the power-on moment, the MCU first reads the temperature element close to the heat source, taking the current temperature as the starting point of drift calculation; then calls the temperature-voltage offset broken line model solidified in the EEPROM, and calculates the accurate voltage correction corresponding to the real-time temperature through linear and cubic spline double algorithm interpolation; the digital quantity is converted into 0-1V microvolt-level analog signal by the 16-bit Σ-Δ DAC in the chip, and is directly superimposed on the feedback node of the PWM control chip to change the reference of the feedback voltage instantaneously; the feedback loop adjusts the duty cycle immediately to correct the output voltage in the direction of offsetting the drift. The entire loop runs continuously with a period of 10ms, and low-pass filtering is performed in advance to remove high-frequency thermal noise, ensuring that each correction is based on clean and stable temperature information, thereby "zeroing" the voltage drift caused by the environment or self-heating in real time, so that the power supply always outputs a stable voltage highly consistent with the set value in the full temperature range.

[0063] Embodiment 3

[0064] In the embodiment, a voltage dynamic calibration method is applied to an adjustable voltage DC power supply circuit, including the following steps:

[0065] When the enable signal M1_EN_PVCOM is detected to be valid, the output voltage of U25 is controlled in the form of step-up;

[0066] Initial stage with 50% duty cycle PWM driving for 10ms;

[0067] Increase 5% duty cycle every 5ms until target voltage. In the segmented soft start method, pause 200us every time the duty cycle is increased by 5%, sample the output voltage and the theoretical value, if the deviation is > 2%, then back off 2% duty cycle and pause again until convergence;

[0068] During the pause, turn off the synchronous rectification MOSFET and use the body diode to freewheel to prevent reverse current impact;

[0069] The number of pauses is written to flash memory for direct skipping of the converged interval segmented soft start next time. The core of the segmented soft start is to increase the PWM duty cycle in steps to avoid voltage surge and inrush current when the power supply starts, protecting the nozzle and circuit elements. The implementation steps are as follows:

[0070] When the control unit detects that the enable signal M1_EN_PVCOM is valid (high), start the soft start program. At this time, the triode Q6 is turned on, and the EN pin (PIN3) of the U25 chip obtains the starting voltage (VEN=VDD_INKET1xR156 / (R149+R156)), and enters the working state.

[0071] Stepwise duty cycle regulation, initial stage: U25 drives the internal MOS tube with a PWM duty cycle of 50% for 10ms. The output voltage is about 50% of the target value (e.g. target voltage 30V, initial output 15V), avoiding large current impact, stepwise increase: increase the duty cycle by 5% every 5ms (e.g. 50%→55%→60%…), until the target duty cycle (corresponding to the target voltage) is reached. For example, with a target voltage of 30V, it takes 10 steps (from 50% to 100%), and the total start-up time is 10ms + 5msx10=60ms, ensuring a smooth voltage rise.

[0072] To avoid overshoot (output voltage exceeding target value) during the stepwise increase process, perform the following steps after each 5% increase in duty cycle:

[0073] Pause and sampling: pause for 200us, sample the output voltage (sent to the ADC module via M1_ADC_VCOM) through the voltage divider module (R148, R153 composed of a voltage divider circuit), calculate the deviation between the actual value and the theoretical value (deviation = (actual value - theoretical value) / theoretical value x 100%).

[0074] Backoff control: If the deviation > 2% (e.g. 20V theoretical, 20.5V actual), backoff 2% duty cycle (e.g. from 60% to 58%), pause sampling again until deviation < 2%.

[0075] Freewheeling protection: During pause, turn off the synchronous rectification MOSFET inside U25, and use Schottky diode D45 for freewheeling, to avoid inductor L9 generating reverse current to shock the load.

[0076] The number of pauses (i.e. the number of adjustment steps needed for convergence) for each soft start will be written to the MCU flash memory. Next time the device is started, the control unit can directly skip the intervals that have already converged (e.g. from 50% to 60% last time without overshoot), and only detect the high duty cycle intervals that are prone to overshoot (e.g. 80%~100%), so that the start-up time is shortened by 30%~50%.

[0077] In this embodiment, the principle of voltage dynamic calibration is to establish a compensation model through the temperature-voltage offset curve, combine RC filtering to suppress noise, use double interpolation algorithm to improve accuracy, and finally realize closed-loop fine tuning through 16-bit DAC, to ensure that the output voltage is not affected by temperature, and when the temperature error is <±0.1℃, the voltage error is <±5mV, which meets the stringent requirements of the nozzle on voltage accuracy (within ±10mV), and the 10ms calibration period can quickly respond to temperature changes, suitable for dynamic scenarios of continuous work of the printer, strong adaptability, 64-segment polyline covering -10℃~60℃, can adapt to the environmental temperature differences in different regions and different seasons.

[0078] The segmented soft start realizes the gentle rise of voltage by stepwise increasing the PWM duty cycle, combined with deviation detection and backoff mechanism, and uses body diode freewheeling protection circuit.

[0079] Achieve the effect of surge suppression, the maximum current during start-up < 1.2 times the rated current (traditional hard start is 3~5 times), avoid overcurrent damage to the nozzle drive chip, and will not cause excessive regulation, the 2% deviation threshold and backoff mechanism ensure that the output voltage is always stable around the target value, without overshoot, start-up acceleration, the number of pauses recorded in the flash memory makes the subsequent start-up skip redundant detection, improving the response speed of the device.

[0080] In this embodiment, the working principle is through four-step closed loop of stepped up, edge up and edge detection, overshoot back and memory acceleration. After the enable signal arrives, the MCU wakes up the power supply with a fixed low duty cycle first, and then gradually increases the code according to the equal-width step. Immediately stop the knife for 200 microseconds after reaching each level, block the reverse impact by using the body diode freewheeling, and sample the output voltage at the same time. If the measured value deviates from the theoretical value by more than the allowed band, immediately back off two levels of duty cycle and verify again, until the deviation converges before continuing to climb. The whole climbing process decomposes the "voltage surge" into multiple "small steps", which not only suppresses the inrush current, but also eliminates the overshoot. The number of back-off required for each convergence is written into the flash memory, and the next start directly skips the verified interval to achieve the purpose of self-learning soft start.

[0081] This embodiment realizes the technical effect of zero-impact power-on. Through stepped up and real-time back-off, the inrush current is compressed to within 1.2 times of the rated value, completely eliminating the electrical stress on the nozzle drive chip, capacitor and wiring caused by the three to five times current of traditional hard start at the moment, significantly prolonging the service life of the device. Secondly, 200 microseconds of micro-stop sampling combined with diode freewheeling not only leaves "thinking" time for the feedback loop, but also blocks the inductive reverse current, so that the synchronous rectifier tube is immune to thermal breakdown, and the overall reliability is improved. Thirdly, the 2% deviation threshold and the step-by-step back-off mechanism lock the overshoot voltage in the safe area of peripheral components, the output curve is smooth and there is no ringing, which avoids the splashing of ink droplets due to high voltage micro-flash of the nozzle, and improves the printing accuracy. Fourthly, the flash memory remembers the convergence steps to realize "two-step start jump", the start time is shortened by 30% to 50% under the same conditions, the device wakes up faster, and the user experience is better. Fifthly, the scheme is realized by pure software without additional thermal elements or high-power resistors, saving BOM cost and PCB area; and the step parameters and deviation threshold can be adjusted online, and the same platform can adapt to different power level power supplies, with strong portability. In summary, this method solves the four contradictions of inrush, overshoot, speed and reliability at a very small cost, providing a simple, efficient and self-learning soft start solution for high-end inkjet devices such as printers and scanners that are sensitive to voltage slope.

Claims

1. An adjustable voltage DC power supply circuit, characterized by: The power input and protection module, the voltage regulation module, the interface and signal regulation module and the voltage division module are included. The power input and protection module is responsible for the input of power, preliminary filtering and overcurrent protection, and is used for controlling the turn-on and turn-off of power and switching control of power. The voltage regulation module provides stable voltage output, and adjusts internal parameters of the module to adapt to different voltage requirements. The interface and signal regulation module processes and adjusts signals through the chip U26, and is used for communication with external devices and data transmission and control with external devices through connection to different signals. The voltage division module is used for generating a stable reference voltage, and provides the reference voltage to the ADC module for accurate analog-digital conversion.

2. The adjustable voltage DC power supply circuit of claim 1, wherein: The power input and protection module includes a fuse F5, one end of the fuse F5 is connected to the ground through a capacitor C129, the capacitor C129 is also connected to VDD_INKET1, the other end of the fuse F5 is connected to the ground through a capacitor C130, the capacitor C130 is also connected to the ground through a capacitor C131, the capacitor C131 is also connected to the junction of the collector of a transistor Q6, a resistor R156 and one end of a capacitor C932, the other ends of the resistor R156 and the capacitor C932 are connected to the ground, the emitter of the transistor Q6 is connected to the ground, the base of the transistor Q6 is connected to the junction of a resistor R154, a resistor R155 and one end of a resistor R157, the other end of the resistor R157 is connected to the ground, the other end of the resistor R154 is connected to VCC3V3M, and the other end of the resistor R155 is connected to M1_EN_PVCOM.

3. The adjustable voltage DC power supply circuit of claim 1, wherein: The voltage regulation module includes a chip U25, a first pin of the chip U25 is connected to an eighth pin of the chip U25 through a capacitor C128, a second pin of the chip U25 is also connected to a resistor R149, a third pin of the chip U25 is connected to one end of a capacitor C932, a fourth pin of the chip U25 is connected to the ground through a resistor R150, seventh and ninth pins of the chip U25 are connected to the ground, a fifth pin of the chip U25 is connected to the junction of a resistor R158 and one end of a resistor R152, a sixth pin of the chip U25 is connected to the junction of a capacitor C137 and one end of a resistor R151, the other end of the resistor R151 is also connected to the ground through a capacitor C138, the other end of the capacitor C137 is connected to the ground, and the eighth pin of the chip U25 is also connected to the junction of a diode D45 and one end of an inductor L9, the other end of the diode D45 is connected to the ground.

4. The adjustable voltage DC power supply circuit of claim 1, wherein: The interface and signal conditioning module, including chip U26, the first pin of the chip U26 is connected to the other end of resistor R158, the second pin of the chip U26 is connected to the junction of capacitor C140, capacitor C141 and VDD_DP_3V3, the capacitor C140 and capacitor C141 are also connected to ground respectively, the third pin of the chip U26 is connected to ground, the fourth pin of the chip U26 is connected to M1_DP_SCK through resistor R161, the fifth pin of the chip U26 is connected to M1_DP_DATA through resistor R162, the sixth pin of the chip U26 is connected to the junction of resistor R159 and M1_DPVCOM_CS through resistor R160, the resistor R159 is also connected to VCC_3V3M, the eighth pin of the chip U26 is connected to ground.

5. The adjustable voltage DC power supply circuit of claim 1, wherein: The voltage dividing module, including inductor L9, the other end of the inductor L9 is connected to the junction of one end of capacitor C132 and the other end of resistor R152, the other end of the capacitor C132 is also connected to ground, the other end of the capacitor C132 is also connected to ground through capacitor C133, the capacitor C133 is also connected to ground through capacitor C134, the capacitor C134 is also connected to the junction of one end of capacitor C135 and VCC_M1_VCCM, the other end of the capacitor C135 is also connected to ground, one end of the capacitor C135 is also connected to LED through resistor R147, LED is also connected to ground, the resistor R147 is also connected to the junction of resistor R148 and one end of capacitor C136, the other end of the capacitor C136 is connected to ground, the other end of the resistor R148 is also connected to the junction of resistor R153, capacitor C139 and M1_ADC_VCOM, the resistor R153 and capacitor C139 are also connected to ground respectively.

6. The adjustable voltage DC power supply circuit of claim 1, wherein: The fuse F5 is a 2A self-recovery fuse, the capacitor C130 and the capacitor C131 are filter circuits for filtering the VDD_INKJET1 power input; the resistor R149 and the resistor R156 constitute a voltage dividing circuit input PIN3 of U25, for setting the starting voltage, the capacitor C932 plays a role in stabilizing the voltage; the resistor R154, the resistor R157, the resistor R155 and the triode Q6 constitute the EN switch circuit of U25; the capacitor C128 is a bootstrap capacitor, and the capacitor C168 is a soft start capacitor; the resistor R150 sets the output PWM frequency; the diode D45 is a Schottky diode; the resistor R158, the resistor R152 and the chip U26 constitute a negative feedback network, which divides the output level and inputs PIN5 of the chip U25 and the reference level for comparison; the resistor R151, the capacitor C137 and the capacitor C138 set the response bandwidth of the internal comparator signal; the chip U26 is a digital potentiometer: AD5160BRJZ10-RL7; VDD_DP_3V3 is the power supply of U26; wherein M1_DP_SCK, M1_DP_VCOM and CSM1_DP_DATA are the clock chip selection and data line of the digital potentiometer.

7. A method for dynamically calibrating voltage, applied to the adjustable voltage DC power supply circuit of any one of claims 1-6, characterized in that, The method comprises the following steps: In each power-on initialization, the control unit reads the data of the sensor; the required correction amount of the reference voltage is calculated according to the preset model; The correction amount is written into the adjustable resistance unit through the digital interface to update the reference value; A low-pass link is added to the sensing channel to filter out high-frequency thermal disturbance, the abstract model is discretized into a data curve and solidified into a non-volatile storage unit, after the non-linear curve is segmented and solidified, the digital compensation value is converted into an analog fine adjustment amount through a double interpolation fusion-high resolution DAC link, and the fine adjustment amount is injected into the feedback loop to realize the real-time closed-loop correction of the reference voltage.

8. The voltage dynamic calibration method of claim 7, wherein, The sensor is a temperature sensor, and the reference reference voltage is compensated according to the temperature-voltage offset curve, specifically including that each time the printer is powered on, the control unit first reads the initial data of the temperature sensor through the I2C or ADC interface, and triggers the calibration program, at this time, the digital potentiometer U26 is reset to the default resistance value, the required correction amount of the reference voltage is calculated according to the preset model, including discretizing the curve into 64 piecewise lines, each corresponding to a temperature interval of 0.5℃, and the node data of the piecewise line of the curve is stored in the EEPROM of the control unit and is not lost after power off.

9. The voltage dynamic calibration method of claim 7, wherein, The writing of the correction amount into the adjustable resistance unit through the digital interface to update the reference value specifically includes writing the compensated resistance value into the digital potentiometer U26 through the SPI interface, the adding of a low-pass link in the sensing path to filter out high-frequency thermal disturbance, the discretization of the abstract model into a data curve and the solidification into a non-volatile storage unit, and the segmented solidification of the non-linear curve, which specifically includes the series connection of an RC low-pass filter with a time constant τ = 100 ms at the output end of the temperature sensor to suppress the instantaneous thermal noise of the print head; the discretization of the temperature-voltage offset curve into 64 piecewise lines and the storage in the MCU EEPROM; and the parallel calculation of linear interpolation and cubic spline interpolation between the piecewise line nodes and the taking of the average value of the two as the compensation value to make the temperature error < ±0.1 °C and the converted voltage < ±5 mV.

10. The method of dynamic voltage calibration of claim 7, wherein, The injection of the fine adjustment amount into the feedback loop to realize the real-time closed-loop correction of the reference voltage specifically includes the conversion of the compensation value into a 0-1 V fine adjustment voltage through a 16 bit Σ-Δ DAC and the superposition on the U25 feedback node to realize the closed-loop calibration.

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