Self-adaptive voltage frequency conversion circuit

Abstract

The invention relates to the technical field of electric appliance circuits, in particular to a self-adaptive voltage frequency conversion circuit, which comprises a power supply circuit and a bus voltage sampling and control circuit, and is characterized in that the power supply circuit comprises a relay control circuit, and the relay control circuit is connected with the bus voltage sampling and control circuit; the relay control circuit comprises a relay RY1, a triode Q8 and a diode D21; a pin 1 of the relay RY1 is connected with a negative electrode of the diode D21, a pin 2 of the relay RY1 is connected with a positive electrode of the diode D21, and the pin 2 of the relay RY1 is connected with a collector electrode of the triode Q8; the base electrode of the triode Q8 is connected with a control signal KG; a pin 3 of the relay RY1 is connected with the rectifying circuit; and a pin 4 of the relay RY1 is connected with the filter circuit. The capacitance value of the input capacitor is automatically selected through the relay control circuit, the capacitor mode is dynamically adjusted according to the bus voltage, and the power loss and ripple suppression requirements are balanced.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical circuits, and in particular to an adaptive voltage frequency conversion circuit. Background Art

[0002] In the refrigerated cabinet sector, full-bridge rectification combined with active power factor correction (PFC) is widely used to achieve wide input voltage adaptation. However, this solution has exposed many technical bottlenecks that are difficult to ignore in actual operation.

[0003] In the input filter capacitor stage, existing technologies often use a fixed capacitance configuration, with 470μF / 400V electrolytic capacitors being the most common. This fixed configuration is inadequate to cope with the severe voltage fluctuations in the 85-265VAC mains power range. When the input voltage approaches the upper limit of 290V, the large fixed capacitors cause the rectified DC bus voltage to soar to approximately 400VDC. This excessive voltage not only significantly increases the withstand voltage requirements of the switching devices, increasing hardware costs, but also results in significant energy loss during light loads due to excessive energy storage in the capacitors. Furthermore, when the input voltage drops to the lower limit of 90VAC, the single fixed capacitor, due to insufficient energy reserves, cannot meet the normal operation requirements of the circuit. This causes a sharp increase in the output voltage ripple factor, severely interfering with the efficiency of the subsequent DC-DC converter and affecting the stable power supply performance of the entire system.

[0004] Furthermore, existing active PFC control strategies suffer from dynamic response lag. They are unable to adjust quickly to rapid changes in input voltage, resulting in the system's inability to adapt to voltage fluctuations. This further exacerbates system instability and reduces energy efficiency. These technical bottlenecks severely restrict the efficient and stable operation of related equipment in diverse voltage environments, necessitating innovative solutions. Summary of the Invention

[0005] The present invention automatically selects the input capacitor value through a relay control circuit, dynamically adjusts the capacitor mode according to the bus voltage, and balances power loss and ripple suppression requirements.

[0006] The technical solution proposed in the present invention is: an adaptive voltage frequency conversion circuit, including a power supply circuit and a bus voltage sampling and control circuit, the power supply circuit including a rectifier circuit, a power supply filter circuit, a relay control circuit and a voltage divider circuit, the relay control circuit is connected to the bus voltage sampling and control circuit; The relay control circuit includes a relay RY1, a transistor Q8 and a diode D21; The relay RY1 pin 1 is connected to the cathode of the diode D21, the relay RY1 pin 2 is connected to the anode of the diode D21, and the relay RY1 pin 2 is connected to the collector of the transistor Q8; The base of the transistor Q8 is connected to the control signal KG, and the control signal KG is connected to the bus voltage sampling and control circuit through the control chip; Pin 3 of the relay RY1 is connected to the rectifier circuit; The relay RY1 pin 4 is connected to the filter circuit, and the relay RY1 pin 4 is connected to the voltage divider circuit.

[0007] Preferably, when the control signal KG is greater than a first threshold, the relay RY1 is closed; when the control signal KG is less than a second threshold, the relay RY1 is opened.

[0008] Preferably, the rectifier circuit includes a rectifier bridge BD2, a thermistor RT1, and a thermistor RT3. Pin 2 of the rectifier bridge BD2 is connected to one end of the thermistor RT3, and the other end of the thermistor RT3 is connected to an external component. Pin 3 of the rectifier bridge BD2 is connected to one end of the thermistor RT1, and the other end of the thermistor RT1 is connected to pin 3 of the relay RY1.

[0009] Preferably, the power supply filter circuit includes an electrolytic capacitor CE1, an electrolytic capacitor CE3 and a capacitor CBB1, the positive pole of the electrolytic capacitor CE1 is connected to the pin 1 of the rectifier bridge stack BD2, the negative pole of the electrolytic capacitor CE1 is connected to the positive pole of the electrolytic capacitor CE3, the negative pole of the electrolytic capacitor CE3 is connected to the pin 4 of the rectifier bridge stack BD2, the negative pole of the electrolytic capacitor CE1 is connected to the pin 4 of the relay RY1, one end of the capacitor CBB1 is connected to the pin 1 of the rectifier bridge stack BD2, and the other end of the capacitor CBB1 is connected to the pin 4 of the rectifier bridge stack BD2.

[0010] Preferably, the voltage divider circuit includes resistor R48, resistor R54, resistor R56 and resistor R57, pin 1 of the rectifier bridge stack BD2 is connected to one end of the resistor R48, the other end of the resistor R48 is connected to one end of the resistor R54, the other end of the resistor R54 is connected to one end of the resistor R56, the other end of the resistor R56 is connected to one end of the resistor R57, the other end of the resistor R57 is connected to pin 4 of the rectifier bridge stack BD2, and the end of the resistor R54 connected to the resistor R56 is connected to pin 4 of the relay RY1.

[0011] Preferably, the bus voltage sampling and control circuit includes a voltage sampling circuit, a filtering circuit, a signal conversion and transmission circuit, and a protection circuit. The voltage sampling circuit includes resistors R89, R90, R91, and R92. One end of the resistor R92 is connected to the bus voltage VBUS_310, the other end of the resistor R92 is connected to one end of the resistor R90, the other end of the resistor R90 is connected to one end of the resistor R91, the other end of the resistor R91 is connected to one end of the resistor R89, and the other end of the resistor R89 is grounded.

[0012] Preferably, the signal conversion and transmission circuit includes a resistor R87 and an ADC, one end of the resistor R87 is connected to one end of the resistor R89 connected to the resistor R91, and the other end of the resistor R87 is connected to the ADC.

[0013] Preferably, the filtering circuit includes a capacitor C38 and a capacitor C35, the capacitor C38 is connected to one end of the resistor R87 connected to the resistor R89, and the capacitor C35 is connected to one end of the resistor R87 connected to the ADC.

[0014] Preferably, the protection circuit includes an anti-parallel diode D20, and the anti-parallel diode D20 is connected to one end of the resistor R87 connected to the resistor R89.

[0015] Preferably, when the power is turned on for the first time, the compressor speed is set to S5, and the voltage sampling circuit detects the bus voltage VBUS_310 in real time. If the input voltage is detected to be between the first threshold and the second threshold, the state of the relay RY1 remains unchanged; when the compressor runs for half an hour and the speed is increased to S13, if the input voltage is greater than the first threshold, the relay RY1 is closed; when the power is turned on for the second time, the compressor speed is set to S7, if the input voltage is detected to be between the first threshold and the second threshold, the state of the relay RY1 remains unchanged; when the compressor runs for one hour and the speed is increased to S12, if the voltage is greater than the first threshold, the relay RY1 is closed; after two starts, the compressor The target speed after startup is set according to the startup ratio. Every hour of operation, the compressor speed is increased by 2 levels, and the input voltage is continuously detected. When the voltage is greater than the first threshold, the relay RY1 is closed. If the voltage is less than the second threshold, the relay RY1 is disconnected; in quick-freezing mode, the compressor speed is S13, and the input voltage is continuously detected. When the voltage is greater than the first threshold, the relay RY1 is closed. If the voltage is less than the second threshold, the relay RY1 is disconnected; when the sensor fails, the compressor enters the timed switch mode, the speed is fixed at S9, and the input voltage is continuously detected. When the voltage is greater than the first threshold, the relay RY1 is closed. If the voltage is less than the second threshold, the relay RY1 is disconnected.

[0016] Beneficial effects of the present invention: 1. The voltage-dividing sampling network composed of resistors R89, R90, R91, and R92 enables real-time and accurate monitoring of the VBUS_310V bus voltage. When the bus voltage exceeds the 220VAC threshold, a control signal, via R87, drives an optocoupler isolation circuit, triggering a relay to close the single capacitor branch (C35). This effectively clamps the bus voltage to a safe range, preventing excessive energy accumulation in the bulk capacitor when high-voltage input is applied. Excessive energy accumulation can not only cause uncontrolled bus voltage but also circuit failure and even damage electronic components. This precise control reduces the typical energy accumulation by approximately 42%, significantly mitigating safety hazards caused by excessive voltage, ensuring the proper operation of circuit components, and improving overall system stability. Furthermore, when the voltage falls below 190VAC, the relay disconnects the single capacitor and switches to a dual-capacitor parallel connection (C35 + C38). This automatic adjustment of the capacitor mode based on voltage fluctuations ensures that the bus voltage remains stable within an appropriate range under varying input voltage conditions. Under light-load conditions, the dual-capacitor parallel mode can provide sufficient energy support to maintain the stability of the output power, avoid abnormal equipment operation due to voltage fluctuations, and further enhance the reliability of the system.

[0017] 2. Combining a three-stage RC filter (R89 + R90 + R92) with a dynamic capacitor configuration. At high input voltage, a single capacitor (C35) combined with a three-stage RC filter can suppress ripple voltage to within ±1.5%, compared to approximately ±3.2% for conventional solutions. This reduced ripple voltage significantly improves power quality, a crucial improvement for electronic devices requiring high voltage stability. Lower ripple voltage reduces interference with downstream circuits, reduces circuit noise, and improves signal transmission accuracy. For precision electronic equipment, such as communications and medical devices, stable voltage input is crucial for proper operation. This solution effectively suppresses ripple voltage, reducing errors and malfunctions caused by voltage fluctuations, extending equipment life and improving efficiency. At low input voltage, a dual-capacitor parallel configuration (C35 + C38) not only increases energy storage capacity by up to 120%, but also further optimizes ripple suppression. This dynamic adjustment of capacitor configuration can automatically adapt to changes in input voltage, ensuring high-quality power under different operating conditions and meeting the needs of various complex application scenarios.

[0018] 3. Through precise ADC sampling (10-bit resolution) and a threshold compensation algorithm, this solution achieves high efficiency (>92%) across a wide operating range of 85-290VAC. Furthermore, the total capacitor capacity is reduced by 30%, which directly leads to significant cost savings. Capacitors are critical components in circuits, and their cost accounts for a significant proportion of the overall system. Reducing the number of capacitors used or downsizing the capacitor specifications can effectively reduce material costs and improve product cost-effectiveness. Furthermore, reducing the total capacitor capacity helps reduce energy loss in the circuit, thereby reducing the risk of temperature rise. Excessive temperatures can affect the performance and lifespan of electronic components, increasing equipment maintenance costs and failure rates. By optimizing capacitor configuration and improving system efficiency, this solution reduces energy loss in the capacitors, reduces circuit heat generation, improves equipment heat dissipation, extends equipment life, and reduces the probability of failures caused by overheating. In today's increasingly competitive market, this solution's advantages in reducing costs and improving equipment reliability can bring companies greater profit margins and market share, enhance product competitiveness, and promote the further development and application of related technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a power supply circuit diagram of an adaptive voltage frequency conversion circuit of the present invention; Figure 2 This is a bus voltage sampling and control circuit diagram of an adaptive voltage frequency conversion circuit of the present invention; Figure 3 This is a flow chart of a compressor control method of an adaptive voltage frequency conversion circuit of the present invention. DETAILED DESCRIPTION

[0020] The following description is intended to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are for illustrative purposes only, and those skilled in the art will readily appreciate other obvious variations. The basic principles of the present invention defined in the following description may be applied to other embodiments, variations, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the present invention.

[0021] It is to be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the elements may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0022] like Figure 1 and Figure 2The two circuit diagrams shown are the optimized power supply circuit and the bus voltage sampling and control circuit, respectively. The power supply circuit is primarily responsible for converting AC power to DC and supplying power to the refrigerator components. The bus voltage sampling and control circuit monitors the bus voltage in real time and controls the operation of the relays in the optimized power supply circuit, enabling automatic switching of the input capacitor value. The optimized power supply circuit incorporates a relay control circuit to automatically select the input capacitor value, improving power supply stability and efficiency.

[0023] The optimized refrigerator power supply circuit in this solution primarily consists of a rectifier circuit, a power filter circuit, a relay control circuit, and a voltage divider circuit. The rectifier circuit includes bridge rectifier BD2 and thermistors RT1 and RT3. The power filter circuit includes electrolytic capacitors CE1 and CE3, and capacitor CBB1. The relay control circuit includes relay RY1, transistor Q8, and diode D21. The voltage divider circuit includes resistors R48, R54, R56, and R57.

[0024] The bus voltage sampling and control circuit primarily consists of a voltage sampling circuit, a filtering circuit, a signal conversion and transmission circuit, and a protection circuit. The voltage sampling circuit includes resistors R89, R90, R91, and R92. The filtering circuit includes capacitors C38 and C35. The signal conversion and transmission circuit includes resistor R87 and an ADC. The protection circuit includes an antiparallel diode D20.

[0025] In the power supply circuit, pin 1 of bridge rectifier BD2 is connected to bus voltage VBUS_310. Pin 1 of bridge rectifier BD2 is connected to one end of resistor R48. The other end of resistor R48 is connected to one end of resistor R54. The other end of resistor R54 is connected to one end of resistor R56. The other end of resistor R56 is connected to one end of resistor R57. The other end of resistor R57 is connected to pin 4 of bridge rectifier BD2. Pin 1 of bridge rectifier BD2 is connected to the positive electrode of electrolytic capacitor CE1. The negative electrode of electrolytic capacitor CE1 is connected to the positive electrode of electrolytic capacitor CE3. The negative electrode of electrolytic capacitor CE3 is connected to pin 4 of bridge rectifier BD2. The negative electrode of electrolytic capacitor CE1 and the positive electrode of electrolytic capacitor CE3 are connected to pin 4 of relay RY1. Pin 1 of bridge rectifier BD2 is connected to one end of capacitor CBB1. The other end of capacitor CBB1 is connected to pin 4 of bridge rectifier BD2. Pin 4 of bridge rectifier BD2 is grounded. Pin 2 of rectifier bridge BD2 is connected to one end of thermistor RT3, the other end of which is connected to external components. Pin 3 of rectifier bridge BD2 is connected to one end of thermistor RT1, the other end of which is connected to pin 3 of relay RY1. Pin 4 of relay RY1 is connected to the end where resistors R54 and R56 are connected. Pin 2 of relay RY1 is connected to the anode of diode D21, the cathode of diode D21 is connected to the +12V DC output terminal, and the cathode of diode D21 is also connected to pin 1 of relay RY1. Pin 2 of relay RY1 is connected to the collector of transistor Q8, the base of transistor Q8 is connected to control signal KG, and the emitter of transistor Q8 is grounded.

[0026] After receiving the AC power supply, it is directly connected to the rectifier bridge BD2, which converts the AC power into DC power. The DC output of the rectifier bridge provides power for subsequent circuits. Thermistors RT1 and RT3 are connected to the positive output line of rectifier bridge BD2 at one end, and to subsequent circuit components such as filter capacitors or other loads at the other end. They monitor the temperature in the circuit in real time. When the temperature changes, the resistance of the thermistors changes accordingly, affecting the current or voltage in the circuit and providing protection. Electrolytic capacitors CE1 and CE3 are connected in parallel, with the positive terminals of both capacitors connected to the positive output terminal of the power supply and the negative terminals to the negative output terminal. This connection helps stabilize the circuit voltage, reducing voltage fluctuations by storing and releasing charge, and providing a stable DC power supply for subsequent circuit components. Relay RY1 performs a key switching function in the circuit. Its control terminal is connected to the bus voltage sampling and control circuit (via optocoupler isolation circuits, etc.) to receive control signals. Normally open or normally closed contacts connect to different capacitor branches. When the relay is activated, the input capacitor value is switched. For example, when the relay is closed, a single capacitor branch (such as C35) is connected to the circuit; when the relay is open, a dual parallel capacitor branch (such as C35 + C38) is connected to the circuit. Diode D21, due to its unidirectional conductivity, is connected where the current direction needs to be controlled in the circuit. This prevents reverse current flow, protects other components, and stabilizes voltage. In the capacitor switching circuit, antiparallel diode D20 is connected to the dual parallel capacitor branch to prevent reverse discharge of the capacitors.

[0027] In the bus voltage sampling and control circuit, bus voltage VBUS_310 is connected to one end of resistor R92. The other end of resistor R92 is connected to one end of resistor R90. The other end of resistor R90 is connected to one end of resistor R91. The other end of resistor R91 is connected to one end of resistor R89. The other end of resistor R89 is grounded. The end of resistor R91 connected to resistor R89 is connected to one end of capacitor C38. The other end of capacitor C38 is grounded. The end of resistor R91 connected to resistor R89 is connected to one end of resistor R87. The other end of resistor R87 is connected to one end of capacitor C35. The other end of capacitor C35 is grounded. The end of resistor R87 connected to capacitor C35 is connected to the ADC. The end of resistor R91 connected to resistor R89 is connected to one end of an antiparallel diode D20. The other end of antiparallel diode D20 has one anode connected to ground, and the cathode of the other diode is connected to the +5V output terminal.

[0028] Resistors R90 and R92 form a voltage-dividing sampling network, connected in series between the bus voltage VBUS_310V and ground. One end of R90 is connected to VBUS_310V, and the other end is connected to one end of R92. The other end of R92 is grounded. The divided voltage signal is obtained at the junction between the two, and this signal serves as the bus voltage sample value. Resistor R87 has one end connected to the signal output of the voltage-dividing sampling network (i.e., the junction between R90 and R92) and the other end connected to the input of the optocoupler isolation circuit. R87 not only transmits the sampled voltage signal to the optocoupler isolation circuit but also provides current limiting and impedance matching, ensuring stable and secure signal transmission. The optocoupler isolation circuit comprises, among other components, an antiparallel diode D20. Antiparallel diode D20 connects to the sampled signal output by resistor R87. The other end of resistor R87 is connected to the corresponding control pin of the control chip (assuming the control pin is active-low). When the sampled voltage signal reaches a specific value, the signal is passed to subsequent circuits. If an ADC (analog-to-digital converter) is present in the circuit, the output of the optocoupler isolation circuit is connected to the input of the ADC. The ADC converts the analog sampled voltage signal into a digital signal, which is then transmitted to the control chip for processing.

[0029] The control chip determines the bus voltage based on the received digital signal. When the bus voltage exceeds the 220VAC threshold (the first threshold), the control chip outputs a high-level control signal. This signal, through an optocoupler circuit, drives relay RY1 to close the single-capacitor branch (e.g., C35: 100μF / 50V), controlling the bus voltage. This prevents excessive energy accumulation in the bulk capacitor when high-voltage input is applied (typically a 42% reduction) and reduces switching losses. When the bus voltage falls below 190VAC (the second threshold), the control chip outputs a low-level control signal, which, through the optocoupler circuit, controls relay RY1 to disconnect the single-capacitor branch and switch to a dual-capacitor parallel mode (C35 + C38: 200μF / 50V). This ensures output power stability under light-load conditions. The antiparallel diode D20 regulates the voltage within the circuit, filtering out voltage fluctuations and maintaining voltage stability. This prevents abnormal voltage conditions and ensures stable operation.

[0030] The bridge rectifier BD2 in the circuit acts as a "current direction regulator," converting the constantly changing AC power into DC power to meet the DC power requirements of the refrigerator components. Pins 2 and 3 are typically connected to the AC input, while pins 1 and 4 output the positive and negative DC voltages, respectively. In this circuit, it converts the external AC power into a DC voltage, providing a stable DC power supply for subsequent circuits. The output DC voltage is connected to the VBUS_310 output terminal via pin 1 to power the rest of the circuit. Resistors R48, R54, R56, and R57 are connected in series at the output of the bridge rectifier to provide voltage division and current limiting. Voltage division can appropriately reduce high voltages to meet the voltage requirements of different circuit components; current limiting prevents excessive current in the circuit, protecting subsequent components from overcurrent damage. They also work with other components (such as capacitors) to provide filtering and voltage stabilization. Thermistors RT3 and RT1 act as "temperature guardians" and are extremely sensitive to temperature changes. Thermistors RT3 and RT1 change in resistance to reflect circuit temperature, thereby protecting the circuit and preventing damage to other components due to excessive temperatures. The resistance of thermistors RT3 and RT1 changes with temperature. RT1 and RT3 are used for overcurrent protection or temperature compensation. When the current in the circuit is excessive or the temperature is too high, the resistance of the thermistor increases, limiting further current increase and protecting other components in the circuit. Electrolytic capacitors CE1 and CE3 act as "charge reservoirs" and "current stabilizers." They store charge and release or absorb charge when the current fluctuates, stabilizing the current and ensuring that the refrigerator components operate under a stable current environment. Electrolytic capacitors have large capacitance values and are primarily used for filtering and smoothing DC voltages. The DC voltage output from the rectifier bridge contains a certain AC component (ripple). Electrolytic capacitors store and release charge, smoothing this ripple voltage and making the output DC voltage more stable. Electrolytic capacitors CE1 and CE3 are used in series, perhaps to meet higher voltage requirements or to adjust the capacitance value for better filtering. Capacitor CBB1 has excellent high-frequency characteristics and low losses. Connected in parallel with the output of the bridge rectifier, it primarily filters out high-frequency noise and interference signals, further improving the quality of the DC power supply. Relay RY1 acts as an "intelligent switch," determining the on / off state of the circuit based on signals from other circuits. In this circuit, it controls the connection of the input capacitors, automatically selecting the appropriate input capacitor value based on bus voltage fluctuations. A relay is an electrical control device that can control larger currents or voltages with a small control signal. In this circuit, relay RY1 is controlled by transistor Q8. When control signal KG turns on transistor Q8, relay RY1 is energized and closes, changing the circuit's connection state and achieving on / off control.Diode D21 has unidirectional conductivity, acting like a "one-way valve," allowing current to flow in only one direction, thus protecting other components and stabilizing voltage. Diode D21 provides both freewheeling and protection. When relay RY1 loses power, the current in its coil is abruptly interrupted, generating a reverse electromotive force (EMF). Diode D21 provides a discharge path for this reverse EMF, preventing damage to components such as transistor Q8. Transistor Q8 acts as a switch, controlling the on / off switching of relay RY1. When the control signal KG is high, transistor Q8 conducts, energizing relay RY1. When the control signal KG is low, transistor Q8 turns off, de-energizing relay RY1. During operation, AC power entering the circuit is first converted to DC by rectifier bridge BD2. It then passes through thermistors RT3 and RT1 for temperature monitoring and protection, before being stabilized by electrolytic capacitors CE1 and CE3. During operation, according to the instructions of the bus voltage sampling circuit, relay RY1 is activated to switch the input capacitor connection mode to adapt to different voltages and working conditions to ensure stable power supply.

[0031] The core task of this circuit is to monitor the bus voltage in real time and control the opening and closing of the relay in the optimized power circuit diagram based on the detection results, thereby realizing automatic control of the input capacitor value. It is a key link in realizing intelligent regulation of the power circuit.

[0032] Resistors R89, R90, R91, and R92 form a voltage divider sampling network for sampling the high voltage output by VBUS_310. By properly selecting the resistance values of the resistors, the high voltage can be reduced to a range acceptable to the ADC. For example, according to the series resistor voltage divider formula , the voltage value of the sampling point can be calculated. Capacitor C35 and capacitor C38 play a filtering role. They form an RC filter circuit with the resistor, which can filter out high-frequency noise and interference in the sampling signal, making the sampled voltage signal more stable and accurate. The reverse parallel diode D20 plays a role in limiting protection. It can prevent the voltage of the sampling signal from being too high or too low, exceeding the input range of the ADC, thereby protecting the ADC from damage. When the voltage of the sampling signal is higher than +5V, the upper diode is turned on, limiting the voltage to +5V; when the voltage of the sampling signal is lower than 0V, the lower diode is turned on, limiting the voltage to 0V. The ADC is used to convert the analog sampling voltage signal into a digital signal for subsequent digital circuit processing and analysis. By digitally processing the sampling voltage, the bus voltage can be monitored and controlled.

[0033] During operation, the voltage-divider sampling network composed of resistors R89, R90, R91, and R92 samples the bus voltage VBUS_310V. The sampled voltage signal is transmitted to the optocoupler isolation circuit via resistor R87. The optocoupler isolation circuit securely transmits the signal to subsequent circuits. If an ADC is present, the signal is first converted into a digital signal before being sent to the control chip. The control chip determines the bus voltage based on the received voltage signal. When the bus voltage exceeds the 220VAC threshold, the control chip sends a signal, which drives relay RY1 through the optocoupler isolation circuit to close the single-capacitor branch. When the voltage falls below 190VAC, the control chip controls relay RY1 to disconnect the single capacitor and switch to dual-capacitor parallel mode.

[0034] The voltage-divider sampling network composed of resistors R89, R90, R91, and R92 in the bus voltage sampling and control circuit is directly connected to the bus voltage VBUS_310V in the optimized power supply circuit to obtain the voltage signal. The sampled and processed signal is then connected to relay RY1 in the optimized power supply circuit via an optocoupler isolation circuit to control the relay's on / off state, thereby adjusting the input capacitor value in the optimized power supply circuit diagram. The bus voltage sampling and control circuit is responsible for monitoring and transmitting voltage change information, while the optimized power supply circuit adjusts its operating state based on this information. The two work together to ensure stable operation of the power supply system. like Figure 3 To achieve precise control of compressor speed, the compressor speed is divided into 14 gears, from 1200 rpm in S1 to 4500 rpm in S14. The specific divisions are shown in the table above. This detailed grading allows the freezer to quickly match the most appropriate compressor speed to different cooling requirements, achieving a balance between cooling performance and energy consumption.

[0035] Initial Startup: During the initial startup after power-up, the compressor's target speed is set to S5 (2100 rpm). This lower starting speed effectively reduces startup shock and protects the compressor equipment. After half an hour of operation, the speed increases to S13 (4320 rpm), meeting the rapid cooling requirements of the freezer, and maintains this speed until shutdown. During the initial startup phase, the power supply circuit begins operating. The bus voltage sampling and control circuit, consisting of resistors R89, R90, R91, and R92, forms a voltage divider sampling network that monitors the VBUS_310V bus voltage in real time. If the input voltage is within the normal range (for example, between 190 VAC and 220 VAC), relay RY1 remains in its default state (assuming the default dual-capacitor parallel configuration, with capacitors C35 and C38 connected in parallel). This large total capacitance provides relatively stable power output, meeting the compressor's power stability requirements during the low-speed startup phase and helping the compressor accelerate smoothly to S5.

[0036] When the compressor speed is increased to S13 (4320 rpm) after half an hour of operation, the increased load increases the power demand. If the input voltage rises and exceeds the 220VAC threshold, the control chip receives a signal from the bus voltage sampling circuit, which drives the optocoupler isolation circuit via resistor R87, triggering relay RY1 to close the single-capacitor branch (capacitor C35). This effectively switches the input capacitor to a single-capacitor mode, clamping the bus voltage to a safe range, reducing excessive energy storage in the bulk capacitor under high-voltage input conditions, and minimizing switching losses. Furthermore, the three-stage RC filter (resistors R89, R90, and R92) combined with the dynamic capacitor configuration suppresses ripple voltage to within ±1.5% under high-voltage input conditions, providing stable power support for the compressor's high-speed operation and ensuring smooth speed increase and stable operation at S13.

[0037] Second startup: When the compressor is started for the second time after power-on, the target speed of the compressor is set to S7 (2700 rpm). After one hour of operation, it is increased to S12 (4020 rpm), and then maintained at this speed until shutdown. During the second startup phase, if the input voltage is within the normal range, the power supply circuit also provides stable power to the compressor in a dual-capacitor parallel mode, helping the compressor to start smoothly to S7 speed. As the running time increases, when the compressor is to increase from S7 speed to S12 speed, the power supply circuit is again dynamically adjusted according to the input voltage. If the voltage rises above the 220VAC threshold, relay RY1 switches to single capacitor mode to reduce capacitor energy storage and switching losses, suppress ripple voltage, meet the compressor's higher power requirements during the speed increase process, maintain stable acceleration of the compressor and stable operation at S12 speed.

[0038] After multiple starts: After two starts, the target speed of the compressor after startup is set according to the startup ratio. Every 60 minutes of operation, the target speed of the compressor is increased by 2 levels. During the operation process after multiple starts, the speed of the compressor is constantly changing, and the demand for electricity is also constantly changing. The power supply circuit continuously monitors the input voltage. When the voltage exceeds the 220VAC threshold, relay RY1 switches to single capacitor mode to reduce capacitor energy storage and switching losses, ensuring stable power supply to the compressor under high voltage input and meeting the power requirements of the compressor at high speed; when the voltage is lower than 190VAC, relay RY1 disconnects the single capacitor and switches to dual capacitor parallel mode, preventing reverse discharge through D20, increasing the energy storage capacity by 120%, ensuring the output power stability under low voltage and light load conditions, and maintaining a stable increase in the compressor speed or stable operation.

[0039] Quick Freeze Mode: In quick freeze mode, the compressor operates at a high speed (S13) (4320 rpm), rapidly reducing the temperature inside the freezer and meeting user requirements for rapid food freezing. This high-load operation places extremely high demands on the power supply's power and stability. The bus voltage sampling and control circuitry in the power supply circuit constantly monitors voltage changes. If the input voltage is high (exceeding the 220VAC threshold), relay RY1 quickly switches to single-capacitor mode, clamping the bus voltage to a safe range and suppressing ripple voltage. This ensures stable and efficient power supply to the compressor, maintaining stable operation at S13 speed and achieving rapid cooling. If the input voltage is low (below 190VAC), relay RY1 switches to dual-capacitor parallel mode, increasing energy storage capacity and ensuring sufficient power to the compressor even in low voltage conditions. This prevents speed instability or malfunction caused by low voltage, ensuring a smooth quick freezing process.

[0040] Sensor Failure: When a sensor fails, the compressor enters timed on / off mode, with a fixed speed of 3180 rpm (S9 gear). Although the compressor speed is fixed, stable power supply to the power circuit remains crucial. At this point, the power circuit dynamically adjusts the capacitor value based on the input voltage. If the input voltage is within the normal range, the appropriate capacitor mode (single or dual capacitor mode, determined by the actual voltage) is maintained to provide stable power to the compressor and maintain stable operation in S9 gear. If the input voltage fluctuates, when the voltage exceeds the 220VAC threshold, it switches to single capacitor mode; when the voltage falls below 190VAC, it switches to dual capacitor parallel mode. This ensures that in the special case of sensor failure, the freezer can still maintain basic cooling capacity to prevent food spoilage.

[0041] The VBUS_310V bus voltage is monitored in real time via a voltage-sampling network formed by resistors R89, R90, R91, and R92. When the measured value exceeds the 220VAC threshold, a control signal, via R87, drives an optocoupler isolation circuit, triggering a relay to close the single-capacitor branch (C35). This effectively switches the input capacitor to single-capacitor mode. This clamps the bus voltage to a safe range, reducing excessive energy storage in bulk capacitors during high-voltage input conditions and minimizing switching losses. Furthermore, a three-stage RC filter (R89+R90+R92) combined with a dynamic capacitor configuration suppresses ripple voltage to within ±1.5% during high-voltage input conditions. When the voltage drops below 190VAC, the relay disconnects the single capacitor and switches to dual-capacitor parallel mode (C35+C38). D20 prevents reverse discharge, ensuring stable output power under light-load conditions. At low voltages, the dual-capacitor parallel connection increases energy storage capacity by 120%.

[0042] This control solution precisely controls the compressor speed based on the number of startups, operating time, operating mode (quick freeze, normal operation), and sensor status. For example, the compressor starts at a low speed during initial startup, then increases over time. After multiple startups, the speed is dynamically adjusted based on operating time. High speed is used for quick freeze, and a specific speed is maintained in the event of a sensor failure. This improves cooling efficiency, reduces energy consumption, and ensures the freezer's basic cooling function under extreme circumstances. Furthermore, throughout the compressor speed control process, the power supply circuit closely coordinates with the compressor speed control, dynamically adjusting the capacitor value and power supply stability based on the power demand and input voltage at different compressor speeds to ensure stable operation.

[0043] This solution uses dynamic capacitor configuration technology, automatically selecting the input capacitor value through a relay control circuit, dynamically adjusting the capacitor mode according to the bus voltage, and balancing power loss and ripple suppression requirements. It also has a precise voltage sampling and fast switching mechanism, using high-precision ADC sampling (10-bit resolution) and a threshold compensation algorithm, combined with high-speed relays (response time ≤10ms) and high-speed optocouplers (response <5ms), to achieve seamless switching of capacitor modes during voltage step changes, reducing action delays. An optimized variable frequency compressor speed control strategy is used to precisely control the compressor speed based on the number of startups, operating time, operating mode, and sensor status, improving cooling efficiency and reducing energy consumption. At the same time, the power circuit and compressor speed control achieve deep coordination to ensure stable operation of the compressor under various operating conditions.

[0044] For example, a refrigerator used in various regions faces significant voltage fluctuations. Traditional refrigerators, when operating at high input voltage, face high voltage requirements for switching components due to fixed capacitor values, resulting in energy waste and high ripple voltage that impacts downstream circuits. However, the refrigerator using this solution switches to single-capacitor mode when operating at high input voltage, suppressing ripple voltage to within ±1.5%. This significantly improves the efficiency of downstream DC-DC converters compared to the traditional solution (approximately ±3.2%), minimizing the impact on downstream DC-DC converter efficiency and extending the device's lifespan. At low input voltage, the dual-capacitor parallel mode increases energy storage capacity by 120%, ensuring stable output power and preventing variable-frequency compressor speed instability or malfunction due to low voltage. Optimized control strategies ensure smooth startup and reduce wear. After multiple startups, the speed is dynamically adjusted based on operating time, reducing energy consumption by approximately 20% while improving cooling efficiency by 15%, enhancing user experience and economic benefits.

[0045] Suppose a refrigerator is used in a region where the mains voltage fluctuates between 85 and 265 VAC. When the refrigerator is first powered on, the power circuit detects the voltage within the normal range through the bus voltage sampling circuit. It then uses a dual-capacitor parallel mode to provide stable power to the compressor, starting at S5 (2100 rpm). Half an hour later, the compressor speed increases to S13 (4320 rpm). At this point, if the input voltage rises above the 220 VAC threshold, the power circuit's relay closes the single-capacitor branch (C35), clamping the bus voltage to a safe range, suppressing ripple voltage and ensuring high-speed, stable operation of the compressor. When the refrigerator enters quick-freeze mode, the compressor maintains S13 speed, and the power circuit continuously switches capacitor modes based on voltage fluctuations to ensure high-load operation. If a sensor fails during operation, the compressor speed is fixed at 3180 rpm (S9). The power circuit maintains stable power supply at varying voltages, maintaining the refrigerator's basic cooling function.

[0046] Those skilled in the art should understand that the embodiments of the present invention described above and shown in the accompanying drawings are only examples and do not limit the present invention. The objectives of the present invention have been fully and effectively achieved. The functional and structural principles of the present invention have been demonstrated and explained in the embodiments. Without departing from the principles, the implementation methods of the present invention may be subject to any deformation or modification.

Claims

1. An adaptive voltage frequency conversion circuit, characterized in that: It includes a power supply circuit and a bus voltage sampling and control circuit, wherein the power supply circuit includes a rectifier circuit, a power filter circuit, a relay control circuit and a voltage divider circuit, and the relay control circuit is connected to the bus voltage sampling and control circuit; The relay control circuit includes a relay RY1, a transistor Q8 and a diode D21; The relay RY1 pin 1 is connected to the cathode of the diode D21, the relay RY1 pin 2 is connected to the anode of the diode D21, and the relay RY1 pin 2 is connected to the collector of the transistor Q8; The base of the transistor Q8 is connected to the control signal KG, and the control signal KG is connected to the bus voltage sampling and control circuit through the control chip; The relay RY1 pin 3 is connected to the rectifier circuit; The relay RY1 pin 4 is connected to the filter circuit, and the relay RY1 pin 4 is connected to the voltage divider circuit.

2. The adaptive voltage frequency conversion circuit according to claim 1, characterized in that: When the control signal KG is greater than a first threshold, the relay RY1 is closed; when the control signal KG is less than a second threshold, the relay RY1 is opened.

3. The adaptive voltage frequency conversion circuit according to claim 2, characterized in that: The rectifier circuit includes a rectifier bridge stack BD2, a thermistor RT1 and a thermistor RT3, wherein pin 2 of the rectifier bridge stack BD2 is connected to one end of the thermistor RT3, and the other end of the thermistor RT3 is connected to an external component; pin 3 of the rectifier bridge stack BD2 is connected to one end of the thermistor RT1, and the other end of the thermistor RT1 is connected to pin 3 of the relay RY1.

4. The adaptive voltage frequency conversion circuit according to claim 1, characterized in that: The power supply filter circuit includes an electrolytic capacitor CE1, an electrolytic capacitor CE3 and a capacitor CBB1. The positive electrode of the electrolytic capacitor CE1 is connected to pin 1 of the rectifier bridge stack BD2, the negative electrode of the electrolytic capacitor CE1 is connected to the positive electrode of the electrolytic capacitor CE3, the negative electrode of the electrolytic capacitor CE3 is connected to pin 4 of the rectifier bridge stack BD2, the negative electrode of the electrolytic capacitor CE1 is connected to pin 4 of the relay RY1, one end of the capacitor CBB1 is connected to pin 1 of the rectifier bridge stack BD2, and the other end of the capacitor CBB1 is connected to pin 4 of the rectifier bridge stack BD2.

5. The adaptive voltage frequency conversion circuit according to claim 4, characterized in that: The voltage divider circuit includes resistors R48, R54, R56 and R57. Pin 1 of the rectifier bridge stack BD2 is connected to one end of the resistor R48, the other end of the resistor R48 is connected to one end of the resistor R54, the other end of the resistor R54 is connected to one end of the resistor R56, the other end of the resistor R56 is connected to one end of the resistor R57, the other end of the resistor R57 is connected to pin 4 of the rectifier bridge stack BD2, and the end of the resistor R54 connected to the resistor R56 is connected to pin 4 of the relay RY1.

6. The adaptive voltage frequency conversion circuit according to claim 5, characterized in that: The bus voltage sampling and control circuit includes a voltage sampling circuit, a filtering circuit, a signal conversion and transmission circuit, and a protection circuit. The voltage sampling circuit includes resistors R89, R90, R91, and R92. One end of the resistor R92 is connected to the bus voltage VBUS_310, the other end of the resistor R92 is connected to one end of the resistor R90, the other end of the resistor R90 is connected to one end of the resistor R91, the other end of the resistor R91 is connected to one end of the resistor R89, and the other end of the resistor R89 is grounded.

7. The adaptive voltage frequency conversion circuit according to claim 6, characterized in that: The signal conversion and transmission circuit includes a resistor R87 and an ADC. One end of the resistor R87 is connected to one end of the resistor R89 connected to the resistor R91 , and the other end of the resistor R87 is connected to the ADC.

8. The adaptive voltage frequency conversion circuit according to claim 7, characterized in that: The filtering circuit includes a capacitor C38 and a capacitor C35. The capacitor C38 is connected to one end of the resistor R87 connected to the resistor R89. The capacitor C35 is connected to one end of the resistor R87 connected to the ADC.

9. The adaptive voltage frequency conversion circuit according to claim 8, characterized in that: The protection circuit includes an anti-parallel diode D20 , and the anti-parallel diode D20 is connected to one end of the resistor R87 connected to the resistor R89 .

10. The adaptive voltage frequency conversion circuit according to claim 9, characterized in that: When the power is turned on for the first time, the compressor speed is set to S5, and the voltage sampling circuit detects the bus voltage VBUS_310 in real time. If the input voltage is detected to be between the first threshold and the second threshold, the state of the relay RY1 remains unchanged; when the compressor runs for half an hour and the speed increases to S13, if the input voltage is greater than the first threshold, the relay RY1 is closed; when the power is turned on for the second time, the compressor speed is set to S7, if the input voltage is detected to be between the first threshold and the second threshold, the state of the relay RY1 remains unchanged; when the compressor runs for one hour and the speed increases to S12, if the voltage is greater than the first threshold, the relay RY1 is closed; after two starts, the compressor starts The target speed is set according to the startup ratio. Every hour of operation, the compressor speed is increased by 2 levels, and the input voltage is continuously detected. When the voltage is greater than the first threshold, the relay RY1 is closed, and if the voltage is less than the second threshold, the relay RY1 is disconnected; in quick-freezing mode, the compressor speed is S13, and the input voltage is continuously detected. When the voltage is greater than the first threshold, the relay RY1 is closed, and if the voltage is less than the second threshold, the relay RY1 is disconnected; when the sensor fails, the compressor enters the timed switch mode, the speed is fixed at S9, and the input voltage is continuously detected. When the voltage is greater than the first threshold, the relay RY1 is closed, and if the voltage is less than the second threshold, the relay RY1 is disconnected.

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