An automatic control system for EDI module current

Abstract

This application discloses an automatic current control system for an EDI module, relating to the field of power supply control. In this system, the output terminal of a high-frequency transformer is connected to the first terminal of a first switching transistor and the positive terminal of the EDI module, respectively; the output terminal of a PWM drive module is connected to the third terminal of the first switching transistor; the second terminal of the first switching transistor is grounded; the first terminal of a second switching transistor is connected to the negative terminal of the EDI module, the positive terminal of a constant current drive module, and the first feedback terminal of the PWM drive module, respectively; the second terminal of the second switching transistor is connected to the input terminal of a sampling resistor, the negative terminal of the constant current drive module, and the second feedback terminal of the PWM drive module, respectively; the output terminal of the constant current drive module is connected to the third terminal of the second switching transistor; and the output terminal of the sampling resistor is grounded. This application eliminates CPU involvement throughout the process, avoiding the need for additional control or communication lines between the EDI module and the motherboard, thus reducing the occurrence of malfunctions.

Description

Technical Field

[0001] This application relates to the field of power control, and in particular to an automatic control system for EDI power supply current. Background Technology

[0002] Electrodeionization (EDI) modules have become a core technology in the "deep desalination" stage of ultrapure water preparation, widely used in semiconductors, photovoltaics, pharmaceuticals, power generation, laboratories, and other scenarios with extremely high water quality requirements. As a standard deep desalination unit in ultrapure water preparation, the EDI module can continuously and stably produce 15–18 MΩcm of high-purity water, while also being environmentally friendly, energy-efficient, and automated. Currently, the common approach to powering the EDI module is to apply an adjustable voltage across its terminals, monitor the EDI current to determine if the voltage is appropriate, and then adjust the voltage using mechanical or electrical methods to meet the EDI power supply requirements.

[0003] Whether it's mechanical voltage regulation (such as manually adjusting a potentiometer) or electrical voltage regulation (such as adjusting via a host computer), the equivalent impedance of EDI increases with usage time. This means that the voltage adjusted on the first day may not meet the requirements by the seventh day, resulting in a low EDI current. Traditional manual potentiometer voltage regulation requires staff to visit the user regularly to adjust the voltage, so this mechanical voltage regulation method was the first to be phased out.

[0004] For electrical voltage regulation, since the EDI current can be monitored, when the monitored EDI current decreases, the motherboard CPU can automatically control the EDI power supply to increase the output voltage until the EDI power supply requirements are met. This method is quite common, but it adds control / communication lines between the EDI power supply and the motherboard. When the motherboard fails, this function will completely fail, resulting in severe coupling. Summary of the Invention

[0005] The purpose of this application is to provide an automatic control system for EDI module current that can automatically control the current of EDI module without the need for CPU intervention, thus avoiding the problem of failure caused by too many connecting wires.

[0006] To achieve the above objectives, this application provides the following solution.

[0007] This application provides an automatic current control system for an EDI module, including: a high-frequency transformer, a first switching transistor, a PWM drive module, a second switching transistor, a constant current drive module, and a sampling resistor.

[0008] The input terminal of the high-frequency transformer is used to input a first DC voltage; the output terminal of the high-frequency transformer is connected to the first terminal of the first switching transistor and the positive terminal of the EDI module, respectively; the input terminal of the PWM drive module is used to input a second DC voltage; the output terminal of the PWM drive module is connected to the third terminal of the first switching transistor; the second terminal of the first switching transistor is grounded; the first terminal of the second switching transistor is connected to the negative terminal of the EDI module, the positive terminal of the constant current drive module, and the first feedback terminal of the PWM drive module, respectively; the second terminal of the second switching transistor is connected to the input terminal of the sampling resistor, the negative terminal of the constant current drive module, and the second feedback terminal of the PWM drive module, respectively; the output terminal of the constant current drive module is connected to the third terminal of the second switching transistor; the output terminal of the sampling resistor is grounded.

[0009] Optionally, the EDI module current automatic control system further includes: an output rectifier and filter module and a dummy load; the high-frequency transformer is connected to the positive terminal of the EDI module through the output rectifier and filter module; the output rectifier and filter module is grounded through the dummy load.

[0010] Optionally, the EDI module current automatic control system further includes: a voltage input module; the voltage input module includes: a power input interface and a power processing module.

[0011] The power input interface is connected to the input terminal of the high-frequency transformer; the power input interface is connected to the input terminal of the PWM drive module through the power processing module; the power input interface is used to input a first DC voltage to the high-frequency transformer; the power processing module is used to process the first DC voltage into a second DC voltage for input to the PWM drive module.

[0012] Optionally, the EDI module current automatic control system further includes: a voltage input module; the voltage input module includes: a power input interface, an input rectification and filtering module, and a power processing module.

[0013] The power input interface is connected to the input terminal of the high-frequency transformer through the input rectification and filtering module; the power input interface is connected to the input terminal of the PWM drive module through the power processing module; the power input interface is used to input AC voltage to the input rectification and filtering module; the input rectification and filtering module is used to rectify the AC voltage into a first DC voltage for input to the high-frequency transformer; the power processing module is used to process the first DC voltage into a second DC voltage for input to the PWM drive module.

[0014] Optionally, the EDI module current automatic control system further includes: a first no-load protection module; the first no-load protection module is connected to the output rectifier and filter module, the EDI module, the second terminal of the second switching transistor, and the PWM drive module.

[0015] Optionally, the EDI module current automatic control system further includes: a second no-load protection module and an isolation module; the second no-load protection module is connected to the output rectifier filter module, the EDI module and the second terminal of the second switching transistor respectively; the second no-load protection module is also connected to the PWM drive module through the isolation module.

[0016] Optionally, the first switching transistor is a MOSFET or a bipolar transistor; wherein, when the first switching transistor is a MOSFET, the first terminal is the drain, the second terminal is the source, and the third terminal is the gate; when the first switching transistor is a bipolar transistor, the first terminal is the collector, the second terminal is the emitter, and the third terminal is the base.

[0017] Optionally, the second switching transistor is a MOSFET or a bipolar transistor; wherein, when the second switching transistor is a MOSFET, the first terminal is the drain, the second terminal is the source, and the third terminal is the gate; when the second switching transistor is a bipolar transistor, the first terminal is the collector, the second terminal is the emitter, and the third terminal is the base.

[0018] Optionally, the constant current drive module includes an operational amplifier.

[0019] Optionally, the output rectification and filtering module includes a rectifier diode.

[0020] Based on the specific embodiments provided in this application, the following technical effects are disclosed.

[0021] This application provides an automatic current control system for an EDI module, including: a high-frequency transformer, a first switching transistor, a PWM drive module, a second switching transistor, a constant current drive module, and a sampling resistor. The high-frequency transformer enables wide voltage output, and the first switching transistor, PWM drive module, second switching transistor, and constant current drive module work together to control the EDI module. While ensuring a constant current in the EDI module, the voltage across the EDI module is dynamically adjusted. The entire process is CPU-free, avoiding the need for additional control or communication lines between the EDI power supply and the motherboard. This prevents the motherboard from failing completely and thus reduces the occurrence of malfunctions. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of an EDI module current automatic control system provided in an embodiment of this application.

[0024] Figure 2 This is a schematic diagram of the EDI module current automatic control system provided in another embodiment of this application when the input power supply voltage is DC.

[0025] Figure 3 This is a schematic diagram of the principle of an automatic current control system for an EDI module when the input power supply voltage is AC, provided as another embodiment of this application.

[0026] Reference numerals: Power input interface-1, High frequency transformer-2, Output rectifier and filter module-3, Power processing module-4, PWM drive module-5, First switching transistor-6, Dummy load-7, Ground-8, Constant current drive module-9, Second switching transistor-10, Sampling resistor-11, First no-load protection module-12, EDI module-13, Input rectifier and filter module-14, Primary ground-15, Isolation module-16, Second no-load protection module-17. Detailed Implementation

[0027] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] The purpose of this application is to provide an automatic control system for EDI module current that can automatically control the current of EDI module without the need for CPU intervention, thus avoiding the problem of failure caused by too many connecting wires.

[0029] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] like Figure 1 As shown, the EDI module current automatic control system provided in this embodiment includes: a high-frequency transformer 2, a first switching transistor 6, a PWM drive module 5, a second switching transistor 10, a constant current drive module 9, and a sampling resistor 11.

[0031] The input terminal of the high-frequency transformer 2 is used to input the first DC voltage; the output terminal of the high-frequency transformer 2 is connected to the first terminal of the first switching transistor 6 and the positive terminal of the EDI module 13, respectively.

[0032] The input terminal of the PWM drive module 5 is used to input the second DC voltage; the output terminal of the PWM drive module 5 is connected to the third terminal of the first switching transistor 6; the second terminal of the first switching transistor 6 is grounded.

[0033] The first terminal of the second switch 10 is connected to the negative terminal of the EDI module 13, the positive terminal of the constant current drive module 9, and the first feedback terminal of the PWM drive module 5, respectively; the second terminal of the second switch 10 is connected to the input terminal of the sampling resistor 11, the negative terminal of the constant current drive module 9, and the second feedback terminal of the PWM drive module 5, respectively; the output terminal of the constant current drive module 9 is connected to the third terminal of the second switch 10; and the output terminal of the sampling resistor 11 is grounded.

[0034] The PWM drive module 5 is used to output PWM waveforms with different duty cycles to drive the first switching transistor 6; the first switching transistor 6 is used to adjust the high-frequency transformer 2 under the drive of the PWM waveform, so that the high-frequency transformer 2 outputs a DC voltage within a set voltage range; the set voltage range is determined based on the first DC voltage.

[0035] In this embodiment, the EDI module current automatic control system drives the first switching transistor through the PWM drive module, causing the high-frequency transformer 2 to output a DC voltage within a set voltage range, thereby achieving a wide range of DC voltage output to the EDI module 13. The first terminal of the second switching transistor 10 performs resistor voltage division on the voltage output from the EDI module 13 and inputs it to the positive terminal of the constant current drive module 9 and the first feedback terminal of the PWM drive module 5, respectively. The second terminal of the second switching transistor 10 is connected to the negative terminal of the constant current drive module 9 and the second feedback terminal of the PWM drive module 5, and the output terminal of the constant current drive module 9 is connected to the third terminal of the second switching transistor 10 to form a loop. When the equivalent impedance of the EDI module 13 increases, the voltage at the first terminal and the voltage at the second terminal of the second switching transistor 10 decrease, and the duty cycle of the PWM waveform output by the PWM drive module 5 increases, thereby increasing the DC voltage output by the high-frequency transformer 2, which in turn increases the voltage across the EDI module 13 until its current reaches the expected value, thus achieving the load matching function. This application achieves wide voltage output function through high-frequency transformer 2, and works with first switching transistor 6, PWM drive module 5, second switching transistor 10 and constant current drive module 9 to control EDI module 13. Under the premise of ensuring constant current of EDI module 13, the voltage across EDI module 13 is dynamically adjusted. The entire process is without CPU participation, avoiding the need to add control lines or communication lines between EDI module 13 and motherboard, so as to prevent the control function from completely failing due to motherboard failure, thus reducing the occurrence of failure.

[0036] In one exemplary embodiment, please refer to Figure 1 The EDI module current automatic control system also includes: output rectifier and filter module 3 and dummy load 7; high frequency transformer 2 is connected to the positive terminal of EDI module 13 through output rectifier and filter module 3; output rectifier and filter module 3 is grounded through dummy load 7; except for EDI module 13, all remaining modules constitute the EDI module current automatic control system.

[0037] In another exemplary embodiment of this application, when the first switching transistor 6 is a MOS transistor, the first terminal is the drain and is connected to the primary winding of the high-frequency transformer 2, the second terminal is the source and is connected to ground 8, which is equivalent to the second terminal of the first switch being the negative terminal of the DC input voltage, and the third terminal is the gate and is connected to the output terminal of the PWM drive module 5; when the first switching transistor 6 is a transistor, the first terminal is the collector and is connected to the primary winding of the high-frequency transformer 2, the second terminal is the emitter grounded, which is the negative terminal of the DC input voltage, and the third terminal is the base and is connected to the output terminal of the PWM drive module 5.

[0038] In another exemplary embodiment of this application, when the second switching transistor 10 is a MOS transistor, the first terminal is the drain and is connected to the negative terminal of the EDI module 13, the second terminal is the source and is connected to the input terminal of the current sampling resistor 11, and the third terminal is the gate and is connected to the output terminal of the constant current driving module 9; when the second switching transistor 10 is a transistor, the first terminal is the collector and is connected to the negative terminal of the EDI module 13, the second terminal is the emitter and is connected to the input terminal of the current sampling resistor 11, and the third terminal is the base and is connected to the output terminal of the constant current driving module 9.

[0039] In another exemplary embodiment of this application, the PWM drive module 5 includes a UC3842 control chip or a TL494 control chip, both of which are classic integrated PWM drive chips.

[0040] In another exemplary embodiment of this application, the constant current drive module 9 includes an operational amplifier.

[0041] In another exemplary embodiment of this application, the output rectification and filtering module 3 includes a rectifier diode. In practical applications, an RC circuit can be added across the rectifier diode.

[0042] In one exemplary embodiment, such as Figure 2 As shown, a schematic diagram of the system of this application is provided when the input power supply voltage is DC. The EDI module current automatic control system also includes: a voltage input module; the voltage input module includes: a power input interface and a power processing module.

[0043] In another exemplary embodiment, please refer to Figure 2 The EDI module current automatic control system also includes: a first no-load protection module 12; the first no-load protection module 12 is connected to the output rectifier filter module 3, the EDI module 13, the second terminal of the second switch tube 10 and the PWM drive module 5 respectively.

[0044] Power input interface 1 is connected to the input terminal of high-frequency transformer 2. Power input interface 1 is used to input a first DC voltage to high-frequency transformer 2. When the input first DC voltage is DC, the DC input voltage supplies power to this system through power input interface 1. The power processing module 4 converts the input DC voltage into voltages such as 5V, 12V, and 15V, which can be used by PWM drive module 5, constant current drive module 9, and first no-load protection module 12, through DC-DC or LDO conversion. High-frequency transformer 2 adopts a secondary-primary winding structure, with the bottom layer being the secondary winding and the top layer being the primary winding. The positive terminal of the DC input voltage is connected to the primary winding of high-frequency transformer 2, and the other end of the primary winding of high-frequency transformer 2 is connected to the first switching transistor 6. The rectangular wave generated by the first switching transistor 6 is applied to the primary winding to achieve electromagnetism. The generated alternating magnetic field passes through the magnetic core and cuts the secondary winding, inducing a voltage on the secondary winding.

[0045] The power input interface is connected to the input terminal of the PWM drive module 5 through the power processing module 4. The power processing module 4 is used to process the first DC voltage into a second DC voltage for input to the PWM drive module 5. The PWM drive module 5 outputs a PWM drive switch 6, which makes the voltage applied to the primary winding of the high-frequency transformer 2 become a rectangular wave. The secondary winding of the high-frequency transformer 2 induces a voltage, which is then rectified and filtered by the output rectifier and filter module 3 to input a fixed DC voltage and output a wide-range DC voltage, which is then connected to ground 8 through a dummy load 7.

[0046] The positive terminal of the DC voltage is connected to the positive terminal of EDI module 13, and the negative terminal of EDI module 13 is connected to the first terminal of the second switching transistor 10. The second terminal of the second switching transistor 10 is connected to the input terminal of the current sampling resistor 11, and the output terminal of the current sampling resistor 11 is connected to ground 8. The positive and negative input terminals of the constant current drive module 9 have the same voltage. The negative input terminal voltage of the constant current drive module 9 is the voltage across the current sampling resistor 11. This voltage is generally 2.5V, 3V, or less than or equal to 3.3V. However, the voltage required at the first terminal of the second switching transistor 10 is usually higher than this voltage. To ensure that it operates in the amplification region, the voltage at the first terminal of the second switching transistor 10 needs to be divided by two resistors to ensure that the voltage at the first terminal is a constant value. The specific value is determined according to the expected constant current value and the datasheet of the first switching transistor 6. For example, the desired voltage at the first terminal of the second switch 10 is 7V, but the negative input voltage of the constant current drive module 9 is only 2.5V, and the positive input voltage is also 2.5V. Therefore, a voltage divider resistor is needed to ensure that the voltage at the first terminal of the second switch 10 is 7V.

[0047] After the above processing, the voltage at the first terminal of the second switch 10 is connected to the positive input terminal of the constant current drive module 9. The voltage at the second terminal of the second switch 10 is the voltage of the current sampling resistor 11 and is connected to the negative input terminal of the constant current drive module 9. The output of the constant current drive module 9 is connected to the third terminal of the second switch 10, forming a small loop. When the output current increases, the voltage across the current sampling resistor 11 increases, the output of the constant current drive module 9 decreases, the voltage at the third terminal of the second switch 10 decreases, its on-resistance increases, and it limits the increase of the output current, and vice versa.

[0048] The voltage at the first terminal of the second switch 10, after the above processing, is connected to the first feedback terminal of the PWM drive module 5, and the other terminal is a reference voltage. The voltage at the second terminal of the second switch 10 is connected to the second feedback terminal of the PWM drive module 5, and the other terminal is a reference voltage, forming a large loop. The two feedback terminals are the positive and negative input terminals of the operational amplifier, respectively. The negative input terminal is connected to the reference voltage, and the positive input terminal is connected to the positive input terminal of the constant current drive module 9, which is the processed voltage at the first terminal of the second switch 10, thus keeping the voltage at the first terminal of the second switch 10 stable. When the voltage at the first or second terminal of the second switch 10 increases, the PWM drive module 5 controls the duty cycle of the output PWM waveform to decrease, thereby reducing the DC voltage rectified and filtered by the output rectifier and filter module 3, and stabilizing the entire circuit. This application uses a PWM drive module 5 with a built-in feedback terminal. The voltage signal is received through the feedback terminal, and the duty cycle of the output PWM is dynamically adjusted according to its internal circuit. If the feedback voltage does not reach the reference value, the duty cycle of the output PWM will be increased, that is, the duty cycle of the rectangular wave voltage applied to the primary winding of the high-frequency transformer 2 will be increased, which will cause the duty cycle of the rectangular wave voltage on the secondary winding to decrease. According to the volt-second balance, the amplitude of the rectangular wave voltage on the secondary winding will increase, and the DC voltage obtained after rectification will naturally increase until the feedback voltage received by the feedback terminal reaches the reference value, and vice versa.

[0049] When the equivalent impedance of EDI module 13 increases, the voltage at the first and second terminals of the second switch 10 decreases. The PWM drive module 5 controls the duty cycle of the output PWM waveform to increase, thereby increasing the DC voltage rectified and filtered by the output rectifier and filter module 3. This causes the voltage across EDI module 13 to rise until its current reaches the expected value, and vice versa, thus achieving load matching. Throughout the process, the voltage at the first and second terminals of the second switch 10 remains consistent, ensuring stable temperature and temperature rise, and preventing damage due to high temperature.

[0050] The input signal of the first no-load protection module 12 is the voltage on the current sampling resistor 11. When the EDI module 13 is disconnected in any way, the system is in a no-load state and the voltage on the sampling resistor 11 becomes 0. At this time, the first no-load protection module 12 will do two things.

[0051] First, the output of PWM driver module 5 is cut off, preventing it from outputting PWM and keeping it at a low level, resulting in an output voltage of 0. Classic integrated PWM driver chips such as UC3842 and TL494, including feedback ports (such as the Vfb port), control the PWM output by connecting the optocoupler control port to a high or low level. The Vfb port provided by the TL494 control chip is the output of the two operational amplifiers responsible for feedback, while the Vfb port provided by the UC384x series chips is the feedback voltage port. Specifically, if the PWM driver module 5 needs to stop working when the Vfb port voltage is high (i.e., not outputting a PWM waveform), then the secondary circuit of the optocoupler needs to apply a high level, such as 5V or 3.3V, to the Vfb terminal of the PWM driver module 5 when both the primary and secondary circuits are conducting, thus stopping its operation, and vice versa.

[0052] Secondly, a very small DC voltage is applied to the output voltage. This DC voltage is the voltage processed by the power processing module 4 and applied to the output terminal through an optocoupler. Alternatively, when the input DC voltage is lower than the 36V human safety voltage, the DC input voltage can be directly connected to the output terminal through an optocoupler.

[0053] The two benefits of accomplishing the above two tasks are: firstly, it enables no-load protection. When the system is unloaded, the output DC voltage will rise. To prevent damage to the EDI module 13 due to excessively high voltage across its terminals after reconnection, the output of the PWM drive module 5 must be cut off. Secondly, it enables hot-swapping. When the EDI module 13 is disconnected for any reason, the above function will take effect. However, when the EDI module 13 is reconnected, since the output voltage has a very small DC voltage, there will be a small voltage across the sampling resistor 11 after reconnection. At this time, the no-load protection module 12 will release the output of the PWM drive module 5, allowing the entire system to resume operation. It will also cut off the small DC voltage previously applied to the output voltage, completing the hot-swapping process, i.e., the entire system changes from being loaded to unloaded and then back to being loaded.

[0054] It is important to note that using a 36V voltage avoids the risk of electric shock if someone accidentally touches an exposed terminal while troubleshooting an unloaded situation. Without this step, if an unloaded state suddenly occurs for some reason, the system can automatically match the load. In this unloaded state, the load could be infinitely large, potentially causing the circuit voltage to spike. In such cases, the PWM output needs to be cut off to reduce the output voltage to 0V to ensure system safety. When the load is reconnected, since this is purely hardware-based, the system will not restart even if the load is reconnected. However, if a small DC voltage is applied after the system transitions from a loaded to an unloaded state and the PWM is cut off, resulting in a 0V output voltage, a small current will be drawn when the load is reconnected. This will also create a voltage across the current sampling resistor 11. The unload protection module 12 will then recognize the system as loaded, reconnect the PWM, and cut off the small DC voltage, allowing the system to resume operation. For automatic control systems, only one input voltage is needed for the system to complete the remaining tasks independently, all handled by hardware. When any electrical system experiences no-load problems for various reasons, it will cause the instrument to malfunction and require additional repair costs. However, the self-recovery function of this application can ensure that the system can still work normally after experiencing load-no-load-load cycles, minimizing the probability of system failure during customer use.

[0055] The wide voltage output function that this application aims to achieve depends primarily on the following factors.

[0056] One aspect is the design of the high-frequency transformer 2 (including the number of turns in the primary and secondary windings and the inductance of the primary winding). This design ensures that the output voltage changes from its minimum to its maximum value as the PWM duty cycle increases. For example, in typical switching power supplies using a flyback topology, the duty cycle of the high-frequency transformer 2 is set to a safe value, such as 35%, to maintain normal operation. The primary and secondary turns ratio is calculated based on the duty cycle, input voltage, and output voltage. However, the output voltage remains constant. This system, however, is a wide-range voltage output system. The actual effect of the PWM duty cycle change is not achieved by the high-frequency transformer design, but rather by the range of the voltage output, which influences the PWM variation and thus the design of the high-frequency transformer.

[0057] According to the volt-second balance formula, (input voltage * duty cycle) / (output voltage * (1 - duty cycle)) = primary / secondary turns ratio, i.e., the number of turns in the primary winding / the number of turns in the secondary winding. Using a general formula for flyback high-frequency transformers, we know that only the input voltage is constant, while the other three are variables. The first is the known minimum and maximum values ​​of the output voltage range; the second is the PWM duty cycle. Considering the influence of temperature, when the ambient temperature drops to 0℃, a too small duty cycle will cause severe PWM distortion; the third is the primary / secondary turns ratio. After the transformer is wound, this physical parameter is considered constant and will not change with the output voltage and duty cycle. Applying the formula, the input voltage remains constant. When the output voltage is at its minimum, the duty cycle is at its minimum, and a primary / secondary turns ratio can be calculated. When the output voltage is at its maximum, the primary / secondary turns ratio remains constant, and the maximum duty cycle can be calculated to achieve wide voltage output.

[0058] One key aspect is that the duty cycle of the PWM signal output by the PWM driver module 5 must support a wide range of variations, while also considering the temperature of the switching transistor 6 to select a reasonable range for the PWM duty cycle. Since the load of this system is EDI, the shorter the usage time, the smaller its equivalent impedance. Under the premise of constant current, the required output voltage is lower. Therefore, this system prioritizes ensuring system stability when the output voltage is very low. In low-temperature environments, the minimum PWM duty cycle is tested to ensure system stability and PWM distortion-free operation even at very low output voltages.

[0059] The present application will now be described in detail through a specific embodiment.

[0060] One EDI module (13) requires a constant current of 180mA and a voltage range of 15~150V, while the entire system requires a 24V power supply. The 24V input is a DC signal input, and the following approach is adopted... Figure 2 The technical solution.

[0061] (1) The PWM duty cycle output by the PWM drive module 5 is set to 20%~72%. When setting this duty cycle range, the minimum value needs to take into account the ambient temperature. Too small a duty cycle will cause serious distortion at 0℃ ambient temperature. The maximum value needs to take into account the temperature and temperature rise of the switching transistor 6. It needs to be verified by experiment.

[0062] (2) Parameter settings for high frequency transformer 2: primary 24T, secondary 54T, primary inductance 160uH.

[0063] (3) When unloaded, simply connect 24V to the positive terminal of EDI module 13 without any further action.

[0064] (4) The sampling resistor 11 has a resistance of 10Ω. Two 20Ω resistors are connected in parallel to prevent the temperature and temperature rise from being too high. In this case, the voltage value on the sampling resistor 11 should be 0.18A*10Ω=1.8V. The two reference voltages of the two feedbacks of the PWM drive module 5 can be adjusted to 1.8V by voltage division of the resistors.

[0065] (5) The rectifier diode in the output rectifier filter module 3 is connected to an RC circuit at both ends, with R value of 135Ω and C value of 220pF. The primary side of the high-frequency transformer 2 is connected to a DRC circuit, with D being a fast recovery diode, R value of 47kΩ and C value of 20nF, which can effectively reduce the ripple of the output voltage / current.

[0066] (6) The core component of the constant current drive module 9 is the LM358 operational amplifier, which can meet the 24V power supply requirements, thus eliminating the need for some DC-DC / LDO circuits.

[0067] (7) When the output voltage is at its minimum, the PWM duty cycle will decrease and the drain-source voltage of the switching transistor 6 will increase. Therefore, a MOSFET with a drain-source voltage greater than 120V should be selected. Other components can be selected with 1.5 to 2 times redundancy, and other parts of the circuit can be built in a conventional manner.

[0068] (8) Apart from EDI module 13, the total material cost of other modules does not exceed RMB 50. An EDI power supply current automatic control system can be built with 24V input and 180mA constant current output to power the EDI. The output voltage will automatically change with the impedance of EDI module 13 to achieve load matching. The range of change is 15~150V to achieve wide voltage output. It also supports hot-swapping, has no-load protection, and the output voltage is 24V when no load is applied. It is safe for human touch.

[0069] The purpose of the automatic control system in this application is to reduce system failures, and the lifespan of the load is a necessary consideration. For loads whose equivalent impedance changes over time, maintaining a constant operating current requires altering the voltage across their terminals, resulting in a wide-voltage output function. When the voltage reaches its upper limit, it indicates that the load's lifespan is nearing its end and its performance is poor. Compared to existing technologies, the wide-voltage output of this system is continuously adjustable, following load changes in real time. It can be used with both new and near-end-of-life loads, requiring no manual or host computer adjustments, resulting in extremely low cost. The unique high-frequency transformer 2 design allows the output voltage to fluctuate around the input voltage; for example, as mentioned in the example, with an input of 24V, the output can vary from 15V to 150V.

[0070] In one exemplary embodiment, such as Figure 3As shown, a technical schematic diagram of an EDI current control system with AC voltage input is provided. The EDI module current automatic control system also includes: a voltage input module; the voltage input module includes: a power input interface 1, an input rectification and filtering module 14, and a power processing module 4.

[0071] The power input interface 1 is connected to the input terminal of the high-frequency transformer 2 through the input rectifier and filter module 14; the power input interface 1 is connected to the input terminal of the PWM drive module 5 through the power processing module 4; the power input interface 1 is used to input AC voltage to the input rectifier and filter module 14; the input rectifier and filter module 14 is used to rectify the AC voltage into a first DC voltage for input to the high-frequency transformer 2; the power processing module 4 is used to process the first DC voltage into a second DC voltage for input to the PWM drive module 5.

[0072] In another exemplary embodiment of this application, the EDI module current automatic control system further includes: a second no-load protection module 17 and an isolation module 16; the second no-load protection module 17 is connected to the second terminal of the output rectifier filter module 3, the EDI module 13 and the second switch tube 10 respectively; the second no-load protection module 17 is also connected to the PWM drive module 5 through the isolation module 16.

[0073] When the input voltage is AC, the input voltage consists of one AC voltage and one DC voltage. The AC voltage serves as the total input of the system, while the DC voltage is used for the second no-load protection module 12. When the system is no-load, the second no-load protection module 12 will cut off the PWM, and the system output voltage will be 0. At this time, a small DC voltage is needed to allow the system to restart, so a DC voltage needs to be added.

[0074] In an exemplary embodiment, the DC input voltage, as the second DC voltage, passes through the power processing module 4 to power the constant current drive module 9 and the second no-load protection module 17. The AC input voltage powers the system through the power input interface 1. The input rectifier and filter module 14 rectifies and filters the AC input voltage to obtain the DC input voltage, which serves as the first DC voltage. This voltage is then converted into a high-frequency rectangular wave by the cooperation of the first switch 6, enabling the high-frequency transformer 2 to operate. The positive terminal of the DC input voltage is connected to the primary winding of the high-frequency transformer 2. The other end of the primary winding of the high-frequency transformer 2 is connected to the first terminal of the first switch 6, and the second terminal of the first switch 6 is connected to the primary ground 15. This means that the second terminal of the first switch 6 is the negative terminal of the DC input voltage.

[0075] As an optional implementation, the PWM drive module 5 outputs a PWM drive to the first switching transistor 6, causing the voltage applied to the primary winding of the high-frequency transformer 2 to become a rectangular wave. The high-frequency transformer 2 supplies power to the PWM drive module 5 through the auxiliary winding. The primary winding induces voltages in the auxiliary and secondary windings according to a certain ratio. The primary winding is the source of the induction, while the voltages on the auxiliary and secondary windings are both obtained through the induction in the primary winding. The voltage induced in the auxiliary winding is rectified and filtered before supplying power to the PWM drive module 5, and is connected to the negative terminal with a -155VDC voltage to ground. The voltage induced in the secondary winding is rectified and filtered before becoming a DC voltage, and is connected to ground 8 through the dummy load 7. The positive terminal of the DC voltage is connected to the positive terminal of the EDI module 13, the negative terminal of the EDI module 13 is connected to the first terminal of the second switching transistor 10, the second terminal of the second switching transistor 10 is connected to the input terminal of the current sampling resistor 11, and the output terminal of the current sampling resistor 11 is connected to ground 8. The voltage at the first terminal of the second switch 10 is processed and connected to the positive input terminal of the constant current drive module 9. The voltage at the second terminal of the second switch 10, i.e., the voltage at the current sampling resistor 11, is connected to the negative input terminal of the constant current drive module 9. The output of the constant current drive module 9 is connected to the third terminal of the second switch 10, forming a small loop. When the output current increases, the voltage across the current sampling resistor 11 increases, the output of the constant current drive module 9 decreases, the voltage at the third terminal of the second switch 10 decreases, its on-resistance increases, and it limits the increase of the output current, and vice versa.

[0076] As an optional implementation, the voltage at the first terminal of the second switching transistor 10 is processed by the isolation module 16 and connected to the first feedback terminal of the PWM drive module 5. The other terminal is the reference voltage. Since the DC input voltage obtained after rectification and filtering of the AC voltage has a negative terminal of -155VDC to ground, the PWM drive module 5 is connected to the negative terminal of -155VDC to ground. However, the constant current drive module 9, the no-load protection module 12, etc. are connected to ground 8. Since some signals connected to these modules and the PWM drive module 5 cannot be directly connected due to the different grounds, the 155V DC voltage will directly damage the chip. Therefore, an isolation module 16 is needed, which is essentially an optocoupler. The optocoupler converts the primary signal connected to ground 8 into a secondary signal connected to the negative terminal, which can then be connected to the PWM drive module 5, and vice versa.

[0077] As an optional implementation, the voltage at the second terminal of the second switch 10, i.e., the voltage of the current sampling resistor 11, is processed by the isolation module 16 and connected to the second feedback terminal of the PWM drive module 5. The other terminal is the reference voltage, forming a large loop. When the voltage at the first or second terminal of the second switch 10 increases, the PWM drive module 5 controls the duty cycle of the output PWM waveform to decrease, thereby reducing the DC voltage rectified and filtered by the output rectifier and filter module 3, thus stabilizing the entire circuit. When the equivalent impedance of the EDI module 13 increases, the voltage at the first and second terminals of the second switch 10 decreases, and the PWM drive module 5 controls the duty cycle of the output PWM waveform to increase, thereby increasing the DC voltage rectified and filtered by the output rectifier and filter module 3, thus increasing the voltage across the EDI module 13 until its current reaches the expected value, and vice versa, to achieve load matching. Throughout the process, the voltage at the first and second terminals of the second switch 10 is consistent, ensuring its temperature and temperature rise are stable and preventing damage due to high temperature.

[0078] As an optional implementation, the input signal of the second no-load protection module 17 is the voltage on the current sampling resistor 11. When the EDI module 13 is disconnected in any form, that is, the system is in a no-load state, the voltage on the sampling resistor 11 becomes 0. At this time, the second no-load protection module 17 will do two things: one is to cut off the output of the PWM drive module 5 through the isolation module 16 so that it cannot output PWM and is always at a low level, at which time the output voltage is 0; the other is to apply a very small DC voltage to the output voltage. The source of this voltage is the DC voltage processed by the power processing module 4 mentioned above.

[0079] The two benefits of accomplishing the above two tasks are: one is to achieve no-load protection. When the system is unloaded, the output DC voltage will rise. To prevent damage to the EDI module 13 due to excessive voltage across its terminals after reconnection, the output of the PWM drive module 5 must be cut off. The other is to achieve hot-swapping functionality. When the EDI module 13 is disconnected for any reason, the above function will take effect. However, when the EDI module 13 is reconnected, since there is a very small DC voltage on the output voltage, there will be a small voltage on the sampling resistor 11 after reconnection. At this time, the no-load protection module 12 will release the output of the PWM drive module 5, allowing the entire system to resume operation, and will cut off the small DC voltage previously applied to the output voltage, thus completing the hot-swapping.

[0080] The wide voltage output function that this application aims to achieve mainly depends on the following factors: one is the design of the high-frequency transformer 2, which can meet the requirement that the output voltage changes from the minimum value to the maximum value when the PWM duty cycle changes from small to large; another is that the duty cycle of the PWM signal output by the PWM drive module 5 must support a wide range of changes, while the temperature of the switching transistor 6 must be taken into account to select a reasonable range of PWM duty cycle.

[0081] This system can be used with both DC and AC inputs, offering flexible compatibility. It supports wide voltage output, hot-swapping, automatic load matching, and no-load protection. The second switch 10 in the constant current section controls the temperature and temperature rise protection devices by controlling the voltage at its first and second terminals. Crucially, all functions are achieved solely through the supply voltage, entirely in hardware without CPU intervention. The constant current output can be achieved by adjusting a few resistors, and the wide voltage range output can be achieved by adjusting the parameters of the high-frequency transformer 2. It is fully compatible with any EDI module 13 at extremely low cost. Furthermore, the voltage value of the sampling resistor 11 is also accessible; dividing this voltage value by the resistance of the sampling resistor 11 yields the EDI current value, which can be detected using a CPU or other means.

[0082] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0083] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the system and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. An automatic current control system for an EDI module, characterized in that, The EDI module current automatic control system includes: a high-frequency transformer, a first switching transistor, a PWM drive module, a second switching transistor, a constant current drive module, and a sampling resistor; The input terminal of the high-frequency transformer is used to input a first DC voltage; the output terminal of the high-frequency transformer is connected to the first terminal of the first switching transistor and the positive terminal of the EDI module, respectively; the input terminal of the PWM drive module is used to input a second DC voltage; the output terminal of the PWM drive module is connected to the third terminal of the first switching transistor; the second terminal of the first switching transistor is grounded; the first terminal of the second switching transistor is connected to the negative terminal of the EDI module, the positive terminal of the constant current drive module, and the first feedback terminal of the PWM drive module, respectively; the second terminal of the second switching transistor is connected to the input terminal of the sampling resistor, the negative terminal of the constant current drive module, and the second feedback terminal of the PWM drive module, respectively; the output terminal of the constant current drive module is connected to the third terminal of the second switching transistor; the output terminal of the sampling resistor is grounded.

2. The EDI module current automatic control system according to claim 1, characterized in that, The EDI module current automatic control system further includes: an output rectifier and filter module and a dummy load; the high-frequency transformer is connected to the input terminal of the EDI module through the output rectifier and filter module; the output rectifier and filter module is grounded through the dummy load.

3. The EDI module current automatic control system according to claim 2, characterized in that, The EDI module current automatic control system further includes: a voltage input module; the voltage input module includes: a power input interface and a power processing module; The power input interface is connected to the input terminal of the high-frequency transformer; the power input interface is connected to the input terminal of the PWM drive module through the power processing module; the power input interface is used to input a first DC voltage to the high-frequency transformer; the power processing module is used to process the first DC voltage into a second DC voltage for input to the PWM drive module.

4. The EDI module current automatic control system according to claim 2, characterized in that, The EDI module current automatic control system further includes: a voltage input module; the voltage input module includes: a power input interface, an input rectification and filtering module, and a power processing module; The power input interface is connected to the input terminal of the high-frequency transformer through the input rectification and filtering module; the power input interface is connected to the input terminal of the PWM drive module through the power processing module; the power input interface is used to input AC voltage to the input rectification and filtering module; the input rectification and filtering module is used to rectify the AC voltage into a first DC voltage for input to the high-frequency transformer; the power processing module is used to process the first DC voltage into a second DC voltage for input to the PWM drive module.

5. The EDI module current automatic control system according to claim 3, characterized in that, The EDI module current automatic control system further includes: a first no-load protection module; the first no-load protection module is connected to the output rectifier and filter module, the EDI module, the second terminal of the second switch and the PWM drive module respectively.

6. The EDI module current automatic control system according to claim 4, characterized in that, The EDI module current automatic control system further includes: a second no-load protection module and an isolation module; the second no-load protection module is connected to the output rectifier filter module, the EDI module and the second terminal of the second switching transistor respectively; the second no-load protection module is also connected to the PWM drive module through the isolation module.

7. The EDI module current automatic control system according to claim 1, characterized in that, The first switching transistor is a MOSFET or a bipolar transistor; wherein, when the first switching transistor is a MOSFET, the first terminal is the drain, the second terminal is the source, and the third terminal is the gate; when the first switching transistor is a bipolar transistor, the first terminal is the collector, the second terminal is the emitter, and the third terminal is the base.

8. The EDI module current automatic control system according to claim 1, characterized in that, The second switching transistor is a MOSFET or a transistor; wherein, when the second switching transistor is a MOSFET, the first terminal is the drain, the second terminal is the source, and the third terminal is the gate; when the second switching transistor is a transistor, the first terminal is the collector, the second terminal is the emitter, and the third terminal is the base.

9. The EDI module current automatic control system according to claim 1, characterized in that, The constant current drive module includes an operational amplifier.

10. The EDI module current automatic control system according to claim 2, characterized in that, The output rectifier and filter module includes: rectifier diodes.

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