An adaptive adjustment-based air conditioning unit conversion efficiency upgrade circuit and its control method

Abstract

This application discloses an adaptive adjustment-based air conditioning unit conversion efficiency upgrade circuit and its control method, relating to the field of air conditioning control technology, to solve the problems of limited space for improving the energy efficiency ratio of existing air conditioning units, slow protection response of frequency converter drive circuits, and weak anti-interference capability. The circuit includes a main control module, a data acquisition module, a drive execution module, and a power management module; the data acquisition module collects the operating parameters and environmental parameters of the air conditioning unit in real time and sends them to the main control module; the main control module internally stores a control algorithm that dynamically calculates the compressor frequency and fan speed based on the operating parameters and environmental parameters; the drive execution module adjusts the power input of the compressor and fan according to the control commands generated by the main control module.

Description

Technical Field

[0001] This application relates to the field of air conditioning control technology, and in particular to an adaptive adjustment-based air conditioning unit conversion efficiency upgrade circuit and its control method. Background Technology

[0002] Air conditioning units are core equipment in modern building environmental control systems and are widely used in residential, commercial, and industrial settings. With rising energy costs and increasing environmental awareness, improving the energy efficiency ratio (SEER / IPLV) of air conditioning units has become an important development direction for the industry.

[0003] Traditional fixed-frequency air conditioning units typically operate at a fixed power level, regulating indoor temperature through an "on-off" cycle. Specifically, the compressor stops running when the indoor temperature reaches the set value; it restarts when the temperature deviates from the set value. While this control method is simple in structure, it is inefficient under partial load. Frequent start-stop cycles not only lead to additional energy consumption but also accelerate wear and tear on the compressor and other mechanical components, shortening the equipment's lifespan. Furthermore, the large current surge during each start-up can negatively impact the power grid.

[0004] To overcome the aforementioned shortcomings of fixed-frequency air conditioners, variable-frequency technology has gradually been adopted. Existing variable-frequency air conditioning units adjust the compressor's operating frequency through an inverter, thereby achieving continuous regulation of cooling capacity and avoiding frequent start-stop cycles. However, the control strategies of most existing variable-frequency air conditioners are relatively fixed, typically adjusting only based on indoor temperature or simple temperature differences. They cannot perform fine-grained adaptive adjustments based on real-time, variable operating conditions (such as indoor-outdoor temperature difference, load rate, and heat exchanger fouling). This results in the air conditioning unit not always operating at its most efficient point during actual operation, especially under partial load or variable operating conditions, limiting the potential for improving the overall energy efficiency ratio.

[0005] In the design of variable frequency drive circuits, existing air conditioning units typically employ a scheme of using optocoupler isolation, discrete gate driver chips, and external discrete components to build the protection circuit. Specifically, after the control signal is electrically isolated by optocouplers, a discrete gate driver chip drives the power switching transistor (such as IGBT); protection functions (such as overcurrent protection and short circuit protection) are implemented through external discrete components such as RC buffer circuits and current sensing resistors. This design scheme has the following problems: First, the circuit structure is complex and the number of components is large, resulting in a cumbersome design and debugging process and poor production consistency; second, the protection circuit composed of discrete components has a slow response speed, usually in the millisecond range, and cannot protect the IGBT in time under severe conditions such as short circuits and bridge arm crosstalk, posing a risk of power device damage or even "explosion"; third, the anti-interference capability of optocoupler isolation and discrete components is relatively weak, and in the high-frequency, high dV / dt noise environment generated by the inverter itself, false protection or false triggering is likely to occur, affecting the stability and reliability of the system.

[0006] Therefore, a new technical solution is needed that can adaptively adjust the air conditioning unit according to its real-time operating parameters and environmental parameters, so that the unit always operates in the high-efficiency range. It should also adopt an integrated and highly reliable variable frequency drive and protection circuit design to achieve fast and accurate protection response and strong anti-interference capability, thereby deeply exploring the energy-saving potential of the air conditioning unit and improving its overall conversion efficiency and operational reliability. Summary of the Invention

[0007] The purpose of this invention is to provide an adaptive adjustment-based air conditioning unit conversion efficiency upgrade circuit and its control method to solve the following problems existing in the prior art: traditional fixed-frequency air conditioning units have low efficiency when operating under partial load, and frequent start-stop operations lead to additional energy consumption and mechanical wear; the control strategies of existing variable-frequency air conditioners are relatively fixed, and they cannot perform fine adaptive adjustment according to real-time and changing operating conditions, thus limiting the potential for improving the overall energy efficiency ratio; existing variable-frequency drive circuits have complex designs, many discrete components, and slow protection response speed, and cannot protect IGBTs in time under severe operating conditions such as short circuits and bridge arm crosstalk, posing a risk of "explosion"; they have weak anti-interference capabilities and are prone to false protection or false triggering in high-frequency, high-dV / dt noise environments generated by the inverter itself.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: Firstly, an adaptive adjustment-based air conditioning unit conversion efficiency upgrade circuit includes: The main control module is used to receive and process sensor data and generate adaptive control commands; The data acquisition module is electrically connected to the main control module and is used to collect the operating parameters and environmental parameters of the air conditioning unit in real time and send the collected data to the main control module. The drive execution module is electrically connected to the main control module and is used to receive the adaptive control command and adjust the power input of the compressor and fan in the air conditioning unit. The power management module is used to provide a stable operating voltage for the main control module, data acquisition module and drive execution module; The main control module internally stores a control algorithm that dynamically calculates the compressor frequency and fan speed based on the operating parameters and environmental parameters.

[0009] Furthermore, the data acquisition module includes a current and voltage detection unit and a temperature detection unit. The current and voltage detection unit is used to collect the operating current and operating voltage of the compressor and fan, and the temperature detection unit is used to collect the indoor ambient temperature, the outdoor ambient temperature, and the temperature of the air conditioner heat exchanger coil.

[0010] Furthermore, the drive execution module includes a frequency converter drive unit and a fan speed control unit. The frequency converter drive unit is connected to the output terminal of the main control module and is used to adjust the operating frequency of the compressor motor according to the control command. The fan speed control unit is connected to the output terminal of the main control module and is used to adjust the operating voltage or pulse width modulation signal of the fan motor according to the control command.

[0011] Furthermore, the frequency conversion drive unit includes an intelligent drive chip, which integrates a desaturation detection circuit, a Miller clamping circuit, and a soft shutdown circuit.

[0012] Furthermore, the frequency conversion drive unit also includes a differential input circuit, which includes a pair of resistors. The differential input circuit is used to convert the PWM control signal from the autonomous control module into a differential signal and send it to the differential input pin of the intelligent drive chip.

[0013] Furthermore, the frequency conversion drive unit also includes a gate drive network, which includes an on-resistor, a off-resistor, and a diode. The resistance value of the on-resistor is greater than the resistance value of the off-resistor, and the diode is used to isolate the on-path and the off-path.

[0014] Furthermore, the frequency conversion drive unit also includes an active Miller clamp circuit, which includes an NPN transistor and a base resistor. One end of the base resistor is connected to the gate of the IGBT, and the other end is connected to the base of the NPN transistor. The collector of the NPN transistor is connected to the gate of the IGBT, and the emitter is connected to the negative drive power supply.

[0015] Furthermore, the frequency conversion drive unit also includes a desaturation protection circuit, which includes a resistor, a capacitor, and a diode. The resistor and the diode are connected in series and then connected between the desaturation detection pin of the intelligent drive chip and the collector of the IGBT. The capacitor is connected in parallel between the desaturation detection pin and the reference ground.

[0016] Secondly, an adaptive adjustment-based air conditioning unit control method includes the following steps: S1: Real-time acquisition of operating parameters and environmental parameters of the air conditioning unit. The operating parameters include the operating current and operating voltage of the compressor and fan. The environmental parameters include indoor ambient temperature, outdoor ambient temperature and air conditioning heat exchanger coil temperature. S2: Based on the collected operating parameters and environmental parameters, combined with the preset air conditioning system model or efficiency MAP, dynamically calculate the compressor target frequency and fan target speed under the current operating conditions; S3: Generates control commands for adjusting the operating frequency of the compressor motor and the speed of the fan motor; S4: Adjust the operating frequency of the compressor motor and the speed of the fan motor according to the control command.

[0017] Furthermore, the efficiency MAP is a two-dimensional lookup table with indoor and outdoor temperature difference and load rate as coordinates. The table stores the optimal compressor frequency and fan speed under the corresponding operating conditions.

[0018] The beneficial effects of this invention are: (1) By collecting multi-dimensional operating data in real time (including the operating current and voltage of the compressor and fan, as well as the indoor ambient temperature, outdoor ambient temperature and air conditioning heat exchanger coil temperature), the optimal operating point of the compressor and fan is dynamically calculated and controlled, so that the air conditioning unit always operates in the high-efficiency range, significantly improving the energy efficiency ratio under partial load and variable operating conditions. Compared with traditional fixed frequency units, it reduces the extra energy consumption and mechanical wear caused by frequent start-stop. (2) The frequency converter drive unit adopts the 1ED3321MC12N intelligent drive chip, which integrates DESAT desaturation protection, active Miller clamping and soft shutdown functions. All protection is completed in a closed loop inside the chip, with a response time of less than 500 nanoseconds, which is much faster than the millisecond response of software protection. It can effectively protect IGBTs under severe conditions such as short circuit and bridge arm crosstalk, reduce the risk of "explosion" to a very low level, and greatly improve the average mean time between failures of the product. (3) The PWM control signal adopts a differential input method, the drive power supply and logic power supply are completely isolated, and the DESAT detection uses a dedicated pin and RC filter. It can work stably in the high frequency and high dV / dt noise environment generated by the inverter itself, and prevent false protection or false triggering caused by interference. It can adapt to complex electromagnetic environment. (4) Highly integrated intelligent driver chips simplify the peripheral circuits, greatly reduce the number of components and PCB area, improve production pass rate, reduce design and debugging complexity, and improve production consistency. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art 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.

[0020] Figure 1 This is a schematic diagram of the structure of the adaptive adjustment-based air conditioning unit conversion efficiency upgrade circuit of the present invention.

[0021] Figure 2 This is a circuit diagram of the frequency conversion drive unit of the present invention.

[0022] The markings in the diagram are as follows: 1. Main control module; 2. Data acquisition module; 21. Current and voltage detection unit; 22. Temperature detection unit; 3. Drive execution module; 31. Variable frequency drive unit; 32. Fan speed control unit; 4. Power management module; 5. Communication module. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0024] like Figure 1 As shown, the adaptive adjustment-based air conditioning unit conversion efficiency upgrade circuit provided by this invention mainly includes a main control module 1, a data acquisition module 2, a drive execution module 3, a power management module 4, and a communication module 5. These modules are electrically connected to form a complete closed-loop control system, enabling real-time perception, intelligent decision-making, and precise execution of the air conditioning unit's operating status.

[0025] The main control module 1 is the core of the entire circuit and can be implemented using an ARM Cortex-M4 series microcontroller. This microcontroller can process multi-channel sensor data at high speed and execute complex adaptive control algorithms. It has an internal adaptive control program that dynamically calculates the compressor target frequency and fan target speed to achieve the optimal overall coefficient of performance (COP) under the current operating conditions, based on real-time collected multi-data (including current, voltage, and multi-point temperature) and a preset thermodynamic model or efficiency map of the air conditioning system. This MAP is calibrated using a large amount of experimental data and stored in the microcontroller's flash memory. The input terminals of the main control module 1 are connected to the data acquisition module 2 via GPIO and ADC interfaces, while the output terminals are connected to the drive execution module 3 and communication module 5 via PWM and UART interfaces, respectively.

[0026] Data acquisition module 2 is responsible for multi-dimensional signal sensing, including current and voltage detection unit 21 and temperature detection unit 22. Current and voltage detection unit 21 uses a Hall current sensor and voltage transformer in conjunction with a signal conditioning circuit, including an operational amplifier, filter capacitor, and protection diode, to accurately acquire the operating current and bus voltage of the compressor motor and fan motor for real-time system power consumption calculation. Temperature detection unit 22 acquires multi-point temperature signals through NTC thermistors located at key locations such as the indoor unit air inlet, outdoor unit heat exchanger inlet and outlet, and compressor exhaust port. The NTC thermistors are connected to the ADC input terminal of main control module 1 via a voltage divider circuit. Main control module 1 converts the ADC sampled values ​​into actual temperature values ​​using a lookup table method. All output signals from data acquisition module 2 are sent to main control module 1 after low-pass filtering and overvoltage protection to ensure signal quality and circuit safety.

[0027] The drive execution module 3 is the control command execution mechanism, including a frequency converter drive unit 31 and a fan speed control unit 32. The frequency converter drive unit 31 receives PWM frequency commands from the main control module 1, drives the three-phase full-bridge inverter circuit, and converts the DC bus voltage into three-phase AC power with adjustable frequency and amplitude to drive the compressor motor. The fan speed control unit 32 receives PWM speed control signals from the main control module 1 and adjusts the fan speed by regulating the duty cycle or output voltage of the fan drive circuit. By coordinating the control of the compressor frequency and fan speed, the dynamic matching of refrigerant circulation flow rate and air volume can be optimized, significantly improving heat exchange efficiency.

[0028] The power management module 4 includes a rectifier circuit, a filter circuit, a buck converter circuit, and a linear regulator circuit connected in sequence, providing isolated power outputs for different modules. The power management module 4 rectifies, filters, bucks, and regulates the AC mains power from the air conditioning unit. This module includes: a rectifier circuit converting AC power to pulsating DC power; a large-capacity filter circuit with capacitors to filter out ripple; a buck converter circuit reducing the DC bus voltage to 24V; and a linear regulator circuit further regulating and outputting multiple power supplies of +15V, +5V, and +3.3V, respectively powering the driver chip, microcontroller, and sensors. Each power output terminal is equipped with LC filtering and overcurrent protection to ensure reliable operation of the entire control circuit.

[0029] The communication module 5 is one of a Wi-Fi module, Bluetooth module, 4 / 5G module, or RS-485 bus interface module. The communication module 5 connects to the main control module 1 via the UART interface of the Wi-Fi module. The communication module 5 can upload real-time operating data of the air conditioning unit, including compressor frequency, fan speed, temperature at various points, current and voltage, energy efficiency ratio (COP), and cumulative operating time, to the cloud platform, and receive remote commands from a mobile APP or management center, such as mode switching, temperature setting, and parameter adjustment. The communication module 5 supports OTA firmware upgrades, facilitating subsequent algorithm optimization and functional expansion.

[0030] Furthermore, it includes a status display and alarm module, which may include LED indicator lights, an LCD display screen and a buzzer, for locally displaying information such as working mode, real-time energy efficiency ratio, and fault codes, and issuing audible and visual alarms when abnormalities such as overcurrent or overtemperature are detected.

[0031] The adaptive adjustment-based air conditioning unit conversion efficiency upgrade circuit provided by this invention can be integrated onto an independent control board. It connects to the existing compressor driver, fan motor, power supply, and sensors of the air conditioning unit via standard interfaces, enabling the upgrade of conversion efficiency for existing air conditioning units (especially fixed-frequency or early variable-frequency units). This adaptive adjustment-based air conditioning unit conversion efficiency upgrade circuit dynamically calculates and controls the optimal operating points of the compressor and fan by collecting multi-dimensional operating data in real time, ensuring the air conditioning unit always operates within its high-efficiency range and significantly improving the energy efficiency ratio under partial load and variable operating conditions. Integrated and modular design: The circuit structure is clear, and the functions of each module are well-defined. It can serve as a built-in control unit for new air conditioning units or as an efficiency upgrade kit for older units, facilitating installation and maintenance. Intelligent and remote management: The optional communication module supports data uploading and remote command reception, providing a hardware foundation for energy efficiency management, fault warning, and maintenance scheduling of unit groups.

[0032] like Figure 2As shown, the core of the frequency converter drive unit 31 is an IGBT high-side gate drive circuit based on the 1ED3321MC12N intelligent drive chip. This circuit integrates signal input, isolated transmission, gate drive, and multiple hardware protection functions, and is a key technical feature of this invention.

[0033] The PWM_UH control signal output by main control module 1 is differentially converted through a pair of 300Ω resistors (R1 and R2). Specifically, the positive terminal of the PWM_UH signal is connected to the IN+ pin (pin 2) of the 1ED3321MC12N chip via R1, and the PWM_UH signal is connected to the IN- pin (pin 3) via R2 after passing through an inverter. The core advantage of this differential input method is that when common-mode noise generated by the power-side switching action is simultaneously coupled to both the IN+ and IN- pins, due to the differential characteristics of the two signals, the differential receiver inside the chip automatically cancels out the common-mode noise, extracting only the differential signal (i.e., the effective PWM control signal), thus achieving extremely strong anti-interference capability.

[0034] The high-voltage side power supply of the 1ED3321MC12N chip is provided by an isolated DC-DC power module. The input of this module is connected to the +5V power supply on the low-voltage side, and the output provides dual power supplies of +15V (VCC2, pin 13) and -8V (VEE2, pin 14). The +15V positive voltage is used for reliable IGBT turn-on, ensuring sufficient gate charge; the -8V negative voltage is used for forced IGBT turn-off, preventing accidental turn-on even in environments with strong interference. A 22μF electrolytic capacitor and a 1μF X7R ceramic capacitor are connected in parallel between the VCC2 and VEE2 pins. The electrolytic capacitor provides large-capacity energy storage, and the ceramic capacitor provides fast transient response; together, they provide a powerful peak current (up to 2A) for the drive pulse. Internally, capacitor isolation technology is used to achieve electrical isolation between the low-voltage side logic signals and the high-voltage side drive output, effectively blocking the impact of high voltage on the control side from the power side.

[0035] The VOUT pin of the 1ED3321MC12N chip outputs a standard gate drive signal: +15V high and -8V low. This signal is connected to the IGBT gate through an asymmetric drive network. The asymmetric drive network consists of an on-state resistor Rgon (10Ω), an off-state resistor Rgoff (4.7Ω), and a high-speed switching diode Dfast. The specific circuit topology is as follows: the VOUT pin is connected to the gate through a series branch of Rgon and Dfast, forming the on-state path; the gate is directly connected back to the VOUT pin through Rgoff, forming the off-state path; the anode of Dfast is connected to VOUT, and the cathode is connected to the junction of Rgon and the gate, ensuring that the on-state current only flows through Rgon and the off-state current only flows through Rgoff. The working principle of this asymmetric design is as follows: When VOUT outputs a high level, the turn-on current flows from VOUT through Rgon and Dfast to the gate. Due to the relatively large resistance of Rgon (10Ω), the turn-on speed is relatively slow, which helps reduce the current spike during IGBT turn-on and the reverse recovery loss of the diode, while also reducing electromagnetic interference. When VOUT outputs a low level, the charge on the gate is quickly discharged to VOUT through Rgoff. At this time, Dfast is reverse-biased and the turn-on path is broken. Due to the relatively small resistance of Rgoff (4.7Ω), the turn-off speed is faster, which helps reduce the turn-off loss of the IGBT and the collector-emitter voltage spike during the turn-off process. By reasonably selecting the resistance values ​​of Rgon and Rgoff, an optimal balance can be achieved between switching losses, voltage stress, and EMI.

[0036] An active Miller clamp circuit is used to prevent the IGBT from being mistakenly turned on during turn-off due to the Miller effect. This circuit consists of a base resistor Rbe (100Ω) and an NPN transistor Q1. One end of Rbe is connected to the gate of the IGBT, and the other end is connected to the base of Q1; the collector of Q1 is connected to the gate, and the emitter is connected to the negative drive power supply VEE2 (-8V). The working principle is as follows: Under normal operating conditions, when the upper IGBT is turned off and the lower IGBT is turned on, the collector voltage of the lower IGBT (i.e., the U-phase output voltage) jumps from a low level to a high level very quickly. This rapid voltage change is coupled to the gate of the upper IGBT through the Miller capacitance Cgc, generating a transient positive coupling voltage. Without the Miller clamp circuit, this coupling voltage may cause the gate potential of the upper IGBT to exceed the turn-on threshold, leading to a mistaken turn-on of the upper IGBT, forming a bridge arm short circuit with the lower IGBT. The instantaneous current can reach thousands of amperes, causing damage to the IGBT. The function of the active Miller clamp circuit is as follows: When the gate GH is coupled and raised due to the Miller effect, a voltage drop is generated across Rbe. When this voltage drop causes the base-emitter voltage Vbe of Q1 to exceed 0.7V, Q1 turns on, forcibly clamping the potential of the gate GH to VEE2 (-8V). The coupled charge is quickly discharged through the collector-emitter channel of Q1. Because Q1 conducts very quickly and has a very low saturation voltage drop, this clamping action can be completed before the Miller coupling voltage rises to a dangerous value, effectively eliminating the risk of false turn-on. The resistance value of Rbe needs to balance sensitivity and stability: too small a resistance value will cause Q1 to be falsely triggered during normal turn-off, while too large a resistance value will reduce the clamping speed. 100Ω is the optimal value verified by experiments.

[0037] The desaturation protection circuit (DESAT) is used to detect whether a short circuit or overcurrent fault occurs during IGBT conduction. This circuit consists of a sense resistor Rdesat (1kΩ), a filter capacitor Cdesat (100pF), and an ultrafast recovery diode Ddesat. One end of Rdesat is connected to the DESAT pin (pin 10) of the 1ED3321MC12N chip, and the other end is connected to the anode of Ddesat; the cathode of Ddesat is connected to the collector C of the IGBT; Cdesat is connected in parallel between the DESAT pin and the source reference ground SH. The working principle is as follows: The 1ED3321MC12N chip integrates a constant current source, which flows out from the DESAT pin. In the normal conduction state of the IGBT, the IGBT operates in the saturation region, and the collector-emitter saturation voltage drop Vce(sat) is very low. At this time, the constant current source current flows to the IGBT collector through Rdesat and Ddesat. When a short-circuit fault occurs (such as a load-side short circuit or bridge arm shoot-through), the current flowing through the IGBT increases sharply, causing the IGBT to exit the saturation region and enter the amplification region, resulting in a sharp rise in Vce. At this time, the cathode potential of Ddesat increases, forcing the constant current source to pull the DESAT pin voltage high. When V_DESAT exceeds the protection threshold of 9V, the internal protection logic of the chip is immediately triggered, performing the following actions: First, a soft shutdown process is initiated, meaning that instead of instantly cutting off the gate drive, the VOUT output voltage is gradually reduced over approximately 1μs, making the IGBT turn-off process relatively smooth and avoiding excessively high voltage spikes that could damage the IGBT due to rapid turn-off; second, after the soft shutdown is completed, the VOUT output is completely blocked, pulling the gate potential to -8V and maintaining it; finally, the / FLT pin (pin 8) is pulled low to output a fault signal, notifying the main control module 1 to enter protection mode. The function of Cdesat is to filter out voltage spikes during IGBT switching, preventing false triggering of the protection. The selection of its capacitance value requires a trade-off between response speed and anti-interference capability: too small a capacitance value will lead to false protection, while too large a capacitance value will delay the protection response time. 100pF is an experimentally optimized value that can control the protection response time within 500ns while ensuring anti-interference capability, which is much faster than software protection. Actual test data shows that this DESAT protection circuit can complete the protection action before the short-circuit current reaches 6 times the IGBT's rated current, effectively preventing IGBT damage due to overcurrent.

[0038] The 1ED3321MC12N chip employs a dual power supply of +15V and -8V. The +15V positive voltage ensures sufficient gate charge when the IGBT is turned on, with the gate-emitter voltage Vge reaching 15V, far exceeding the IGBT's turn-on threshold. Even with some parasitic inductance and resistive losses in the gate drive circuit, it guarantees full IGBT conduction, reducing conduction losses. The -8V negative voltage ensures the IGBT gate is forcibly pulled to a negative potential when turned off, forming a reliable reverse bias. Even in environments with strong interference, it prevents the IGBT from being falsely turned on. Compared to the traditional 0V turn-off method, negative voltage turn-off increases the noise margin by 8V, significantly improving the circuit's anti-interference capability. To further protect the IGBT gate from overvoltage damage, an 18V Zener diode DZ1 is connected in parallel between the gate GH and the source SH. The function of this Zener diode is to clamp the gate voltage at 18V when the gate voltage exceeds 18V due to abnormal conditions, such as a driver circuit failure or external interference. This prevents permanent damage caused by exceeding the maximum rated gate voltage of the IGBT. Simultaneously, a 10kΩ pull-down resistor R_pulldown is connected in parallel between the gate (GH) and the source (SH). The function of this resistor is to reliably pull the gate potential to the source potential (0V) when the driver circuit is not working, such as during the initial power-on of the system or when the driver chip fails, forcing the IGBT to be in the off state and achieving a "fail-safe" function. The selection of the 10kΩ resistor value requires a trade-off between static power consumption and pull-down capability: a too-small resistance value will increase the static power consumption of the driver circuit, while a too-small resistance value will reduce the pull-down capability. 10kΩ is an empirical value used in engineering practice.

[0039] The source sensing pin SH of the IGBT module is a critical reference point for the high-side drive circuit. This pin is directly connected to the emitter E of the upper transistor inside the IGBT module (not the negative DC bus N). The VSS2 pin (pin 14, i.e., the reference ground of the negative drive power supply VEE2), the return path of the VOUT pin, and the reference ground of the DESAT protection circuit of the 1ED3321MC12N chip must all be connected to the SH pin. The core significance of this connection method is to ensure that the drive circuit is an independent closed loop with the smallest area and the lowest parasitic inductance, unaffected by the large current changes in the main power circuit. Specifically, when the IGBT switches, a transient current of several hundred amperes flows through the main power circuit. If the reference ground of the drive circuit is incorrectly connected to the negative DC bus N, this induced voltage will be superimposed on the drive signal, causing serious interference or even false triggering. By connecting the reference ground of the drive circuit to the SH pin, i.e., the local emitter of the IGBT, the drive circuit and the main power circuit achieve "star grounding", effectively isolating the interference of the main power circuit. Actual test data shows that by using the correct SH connection method, the noise amplitude of the drive signal can be reduced by more than 80%.

[0040] The work process is as follows: (a) Normal operating procedure After the system is powered on, the power management module 4 first supplies power to each module. The main control module 1 completes self-test and initialization (including ADC calibration, PWM timer configuration, and communication module connection), and then enters the main loop. In the main loop, the main control module 1 executes the following steps with a period of 100ms: First, it reads the current operating parameters and environmental parameters through the data acquisition module 2, including compressor current Icomp, compressor voltage Vcomp, fan current Ifan, fan voltage Vfan, indoor temperature Tin, outdoor temperature Tout, heat exchanger inlet temperature Thi, heat exchanger outlet temperature Tho, and compressor discharge temperature Tdis; Second, it calculates the current system power consumption Ptotal = Vcomp × Icomp + Vfan × Ifan, and the heat exchanger heat transfer Q = m × Cp × (Thi - Tho) based on the acquired data (where m is the refrigerant mass flow rate and Cp is the specific heat capacity, both of which are known constants or calculated through empirical formulas); Third, based on the current indoor-outdoor temperature difference ΔT = Tout - Tin and the heat transfer Q, it queries the preset efficiency MAP chart to determine the compressor target frequency fcomp_target and fan target speed nfan_target that maximize the coefficient of performance COP = Q / Ptotal under the current load. The efficiency MAP is a two-dimensional lookup table calibrated using a large amount of experimental data. The horizontal axis represents the indoor-outdoor temperature difference ΔT (range -10℃ to +50℃, step size 2℃), and the vertical axis represents the load rate (range 20% to 100%, step size 10%). Each cell in the table stores the optimal compressor frequency and fan speed under the corresponding operating condition. The fourth step involves generating PWM control commands. The inverter drive unit 31 smoothly transitions the compressor frequency from the current value fcomp_current to the target value fcomp_target (transition time 10 seconds to avoid mechanical and current shocks caused by sudden changes). The fan speed control unit 32 smoothly transitions the fan speed from the current value nfan_current to the target value nfan_target (transition time 5 seconds). The fifth step involves uploading the current operating data (including sensor readings, calculated COP value, and cumulative operating time) to the cloud platform via the communication module 5 and checking for any remote commands that need to be executed. The entire control process forms a closed loop of "perception-decision-execution-feedback," ensuring that the air conditioning unit always operates at its most efficient operating point.

[0041] At the circuit level of the frequency converter drive unit 31, the normal operating procedure is as follows: The PWM_UH signal output by the main control module 1 is differentially converted and sent to the IN+ and IN- pins of the 1ED3321MC12N chip. The differential receiver inside the chip extracts the differential signal and transmits it to the high-voltage side through capacitor isolation. The output stage on the high-voltage side controls the VOUT pin to output the corresponding level according to the state of the input signal: when the input is high, VOUT outputs +15V; when the input is low, VOUT outputs -8V. The VOUT signal acts on the IGBT gate GH via an asymmetric gate drive network: During turn-on, the +15V voltage charges the gate through Rgon (10Ω) and Dfast for approximately 150ns. The gate voltage Vge rises to 15V, the IGBT turns on, and the collector-emitter saturation voltage drop Vce(sat) drops to 2-3V, causing the compressor motor to start. During turn-off, the gate charge is rapidly discharged to VOUT (at -8V) through Rgoff (4.7Ω) for approximately 80ns. The gate voltage Vge drops to -8V, the IGBT reliably turns off, and the collector-emitter voltage Vce rises to the DC bus voltage of 300V, allowing the compressor motor to freewheel. Throughout the switching process, the DESAT protection circuit continuously monitors the IGBT's Vce: Since the IGBT operates in the saturation region, Vce(sat) remains at 2-3V, and the DESAT pin voltage is approximately 3.2V, far below the protection threshold of 9V, keeping the protection circuit in standby mode. The active Miller clamp circuit monitors the gate voltage during IGBT turn-off: because the voltage amplitude of dV / dt generated by the lower transistor turning on is very small and coupled to the gate of the upper transistor through the Miller capacitance, it is insufficient to turn on Q1, and the clamp circuit does not operate. Through the above coordinated operation, the frequency converter drive unit 31 achieves accurate and reliable driving of the IGBT.

[0042] (II) Fault Protection Mechanism When a system experiences a short circuit, overcurrent, or bridge arm crosstalk fault, the hardware protection circuit will automatically trigger and execute a rapid protection action. Taking a short circuit fault as an example, suppose that at a certain moment, due to an unexpected short circuit at the load end (such as compressor winding insulation breakdown), the current flowing through the IGBT rises sharply from the rated value (e.g., 50A) to hundreds of amperes within microseconds. Due to the excessive current, the IGBT exits the saturation region and enters the amplification region, and the collector-emitter voltage Vce rises sharply (from 2-3V to tens of volts within hundreds of nanoseconds). At this time, the DESAT protection circuit works as follows: First, due to the increase in Vce, the cathode potential of Ddesat increases, and the constant current source inside the 1ED3321MC12N chip is forced to pull the voltage of the DESAT pin high; when V_DESAT exceeds the protection threshold of 9V, the comparator inside the chip flips, triggering the protection logic; the protection logic immediately initiates a soft shutdown process, that is, gradually reducing the VOUT output voltage within about 1μs, so that the gate voltage of the IGBT slowly drops from +15V to -8V, rather than being cut off instantaneously. This soft turn-off method can control the di / dt during the turn-off process within a reasonable range (e.g., 1000A / μs), avoiding excessively high voltage spikes on the parasitic inductance due to excessively fast turn-off. After the soft turn-off is completed, the chip completely blocks the VOUT output, maintaining the gate potential at -8V to ensure reliable IGBT turn-off. Simultaneously, the chip pulls the / FLT pin low, outputting a low level of 0V. This signal is sent to the interrupt input of the main control module 1 after optocoupler isolation, triggering the interrupt service routine. The main control module 1 performs the following protection measures in the interrupt service routine: immediately stops all PWM outputs and blocks the drive signals of all bridge arms; records the fault code and operating parameters at the time of the fault, including sensor readings and control commands before the fault, to the EEPROM; reports the fault information to the cloud platform through the communication module 5; illuminates the fault indicator light and sounds a buzzer alarm; and enters the fault protection mode, waiting for manual or remote reset commands. From the occurrence of a short circuit to the IGBT's turn-off, the entire protection process is completed within 500ns. This protection response time is thousands of times faster than software protection (which typically takes several milliseconds), effectively preventing IGBT damage due to overcurrent. Actual measurement data shows that the hardware protection circuit can complete the protection action before the short-circuit current reaches six times the IGBT's rated current. The IGBT's junction temperature rise is less than 10℃, far below its maximum allowable junction temperature, ensuring the safety of the power device.

[0043] For bridge arm crosstalk faults, specifically the high dV / dt generated when the lower IGBT turns on, causing the upper IGBT to mis-turn on, the protection process of the active Miller clamp circuit is as follows: When the lower IGBT turns on rapidly, its collector voltage (i.e., the U-phase output voltage) jumps from a low level to a high level at an extremely fast speed. This rapid voltage change is coupled to the gate of the upper IGBT through the Miller capacitance Cgc, generating a transient positive voltage. Without the Miller clamp circuit, this coupled voltage may cause the gate potential of the upper IGBT to exceed the turn-on threshold (approximately 5V), leading to mis-turn-on of the upper IGBT and forming a bridge arm shoot-through short circuit with the lower IGBT. The operation of the active Miller clamp circuit is as follows: When the gate GH is coupled and raised due to the Miller effect, a voltage drop is generated across Rbe (100Ω); when this voltage drop causes the base-emitter voltage Vbe of Q1 to exceed 0.7V, Q1 turns on; after Q1 turns on, its collector-emitter channel forms a low-impedance path, forcibly clamping the potential of the gate GH to VEE2 (-8V), and the coupled charge is quickly discharged through Q1; since the switching speed of Q1 is extremely fast (<10ns), this clamping action can be completed before the Miller coupling voltage rises to a dangerous value, effectively eliminating the risk of mis-enabling. Measured data shows that in a bridge arm crosstalk environment with dV / dt as high as 10kV / μs, after using the active Miller clamp circuit, the maximum fluctuation amplitude of the upper transistor's gate voltage is less than 1V, far below the turn-on threshold, completely eliminating the risk of bridge arm shoot-through short circuit.

[0044] To verify the technical effects of this invention, two identical split-type air conditioning units (cooling capacity 3500W, rated power 1200W) were used as the test subjects. The control group used fixed-frequency control, while the experimental group was equipped with the conversion efficiency upgrade circuit of this invention. Tests were conducted in a standard environmental chamber (indoor 27℃, outdoor 35℃). Energy efficiency test results showed that under 50% load conditions, the experimental group had an average input power of 520W, while the control group had 650W, resulting in an energy saving rate of 20%; under 75% load conditions, the experimental group had 820W, while the control group had 950W, resulting in an energy saving rate of 14%; under 100% load conditions, the power of both was similar, with an energy saving rate of approximately 5%. Regarding temperature control, the experimental group's temperature fluctuation range was 26.8-27.2℃, while the control group's was 26.5-27.5℃, demonstrating a significant improvement in control accuracy. In the protection response test, under a short-circuit fault, the DESAT protection circuit completed the IGBT shutdown within 480ns, and the IGBT remained undamaged in 100 tests. In the anti-interference test, the differential input circuit operated stably in a common-mode noise environment without any false protection or false triggering.

[0045] In summary, this invention, by collecting multi-dimensional operational data in real time and dynamically adjusting the operating points of the compressor and fan, ensures that the air conditioning unit always operates within its high-efficiency range, significantly improving the energy efficiency ratio under partial load and variable operating conditions. By employing the 1ED3321MC12N intelligent drive chip and integrating multiple hardware protection functions such as DESAT protection and active Miller clamping, it achieves fast and reliable protection for the IGBT, greatly improving system reliability. Furthermore, by adopting anti-interference designs such as differential input and asymmetric gate drive, it ensures stable operation of the system in complex electromagnetic environments. This invention can be used as an integrated control unit in new air conditioning units or as an efficiency upgrade kit for older units, demonstrating broad application prospects.

[0046] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. An air conditioning unit conversion efficiency upgrade circuit based on adaptive adjustment, characterized in that, Comprise: The main control module is used for receiving and processing sensor data and generating adaptive control instructions; The data acquisition module is electrically connected with the main control module, and is used for collecting running parameters and environmental parameters of the air conditioning unit in real time and sending the collected data to the main control module; The drive execution module is electrically connected with the main control module, and is used for receiving the adaptive control instructions and adjusting the power input of the compressor and the fan in the air conditioning unit; The power management module is used for providing stable working voltage for the main control module, the data acquisition module and the drive execution module; Wherein, the main control module internally stores a control algorithm for dynamically calculating the frequency of the compressor and the rotating speed of the fan according to the running parameters and the environmental parameters.

2. The adaptive adjustment based air conditioning unit conversion efficiency upgrade circuit of claim 1, wherein, The data acquisition module comprises a current and voltage detection unit and a temperature detection unit, the current and voltage detection unit is used for collecting the working current and working voltage of the compressor and the fan, and the temperature detection unit is used for collecting the indoor environmental temperature, the outdoor environmental temperature and the air conditioner heat exchanger coil temperature.

3. The adaptive adjustment based air conditioning unit conversion efficiency upgrade circuit of claim 1, wherein, The drive execution module comprises a frequency conversion drive unit and a fan speed regulation unit, the frequency conversion drive unit is connected with the output end of the main control module, and is used for adjusting the working frequency of the compressor motor according to the control instructions, and the fan speed regulation unit is connected with the output end of the main control module, and is used for adjusting the working voltage or pulse width modulation signal of the fan motor according to the control instructions.

4. The adaptive adjustment based air conditioning unit conversion efficiency upgrade circuit of claim 3, wherein, The frequency conversion drive unit comprises an intelligent drive chip, the intelligent drive chip internally integrates a desaturation detection circuit, a Miller clamp circuit and a soft shutdown circuit.

5. The adaptive adjustment based air conditioning unit conversion efficiency upgrade circuit of claim 4, wherein, The frequency conversion drive unit further comprises a differential input circuit, the differential input circuit comprises a pair of resistors, and the differential input circuit is used for converting the PWM control signal from the main control module into a differential signal and sending the differential signal into the differential input pin of the intelligent drive chip.

6. The adaptive adjustment based air conditioning unit conversion efficiency upgrade circuit of claim 4, wherein, The frequency conversion drive unit further comprises a gate drive network, the gate drive network comprises a turn-on resistor, a turn-off resistor and a diode, the resistance value of the turn-on resistor is greater than that of the turn-off resistor, and the diode is used for isolating the turn-on path and the turn-off path.

7. The adaptive adjustment based air conditioning unit conversion efficiency upgrade circuit of claim 4, wherein, The frequency conversion drive unit further comprises an active Miller clamp circuit, the active Miller clamp circuit comprises an NPN triode and a base resistor, one end of the base resistor is connected to the gate of the IGBT, the other end is connected to the base of the NPN triode, the collector of the NPN triode is connected to the gate of the IGBT, and the emitter is connected to the negative driving power supply.

8. The adaptive adjustment based air conditioning unit conversion efficiency upgrade circuit of claim 4, wherein, The frequency conversion drive unit further comprises a desaturation protection circuit, the desaturation protection circuit comprises a resistor, a capacitor and a diode, the resistor and the diode are connected in series and then connected between the desaturation detection pin of the intelligent drive chip and the collector of the IGBT, and the capacitor is connected in parallel between the desaturation detection pin and the reference ground.

9. A method of controlling an air conditioning unit based on adaptive adjustment, the method comprising: The method comprises the following steps: S1: collecting running parameters and environmental parameters of the air conditioning unit in real time, the running parameters comprising the working current and working voltage of the compressor and the fan, and the environmental parameters comprising the indoor environmental temperature, the outdoor environmental temperature and the air conditioner heat exchanger coil temperature; S2: dynamically calculating a target frequency of the compressor and a target rotating speed of the fan under the current working condition according to the collected operating parameters and environmental parameters, in combination with a preset air conditioning system model or efficiency MAP graph; S3: generating a control instruction for adjusting the working frequency of the compressor motor and the rotating speed of the fan motor; S4: adjusting the working frequency of the compressor motor and the rotating speed of the fan motor according to the control instruction.

10. The method of claim 9, wherein, The efficiency MAP graph is a two-dimensional lookup table taking the indoor-outdoor temperature difference and the load rate as coordinates, and the optimal compressor frequency and fan rotating speed under the corresponding working condition are stored in the table.

Images