Over-current protection method, over-current protection circuit power supply circuit and air conditioner outdoor unit

Abstract

The invention discloses an overcurrent protection method, an overcurrent protection circuit, a power supply circuit and an air conditioner outdoor unit, and belongs to the technical field of power electronics. The overcurrent protection method comprises the following steps: acquiring an instantaneous current value of the power factor correction circuit; periodically determining a corresponding first overcurrent protection threshold value according to the instantaneous current value, wherein the first overcurrent protection threshold value is greater than the instantaneous current value of the corresponding period; and executing an overcurrent protection strategy on the power factor correction circuit according to the first overcurrent protection threshold. The corresponding overcurrent protection threshold value is generated on the basis of the actual current of the circuit, so that the current accessed to the outdoor unit of the air conditioner has different overcurrent protection threshold values at different current phases, thereby reducing the difference of overcurrent trigger intervals at different phases, improving the reliability of overcurrent protection, and improving the reliability of overcurrent protection. And the equipment safety of the air conditioner outdoor unit is protected.

Description

Technical Field

[0001] This application belongs to the field of power electronics technology, and in particular relates to an overcurrent protection method, an overcurrent protection circuit power supply circuit, and an outdoor unit of an air conditioner. Background Technology

[0002] The outdoor unit of an air conditioner is an important component of an air conditioning system, typically installed outdoors, opposite the indoor unit. The outdoor unit houses components such as the compressor, and a power circuit is installed within it to ensure power supply to these components. This power circuit usually includes a power factor correction circuit to reduce energy loss and improve the stability and reliability of the power supply.

[0003] To ensure the safety of air conditioner outdoor units, power factor correction circuits typically include overcurrent protection mechanisms to promptly cut off power and shut down the unit in case of overcurrent. Currently, current ripple is observed through measured data, and a few amps are added as a safety threshold based on empirical values. The real-time current of the power factor correction circuit is then compared to this threshold, and an overcurrent is detected when the actual current is greater than or equal to the threshold. However, air conditioner outdoor units use AC power, which has large current amplitude variations, and the power supply is usually AC mains power, which is itself subject to fluctuations. Therefore, the reliability of current overcurrent protection schemes is relatively low. Summary of the Invention

[0004] This application aims to at least solve one of the technical problems existing in the prior art. To this end, this application proposes an overcurrent protection method, an overcurrent protection circuit power supply circuit, and an outdoor unit for air conditioning. The power factor correction circuit has different overcurrent protection thresholds at different current phases, which improves the reliability of overcurrent protection and protects the equipment safety of the outdoor unit for air conditioning.

[0005] In a first aspect, this application provides an overcurrent protection method for a power factor correction circuit, comprising:

[0006] Obtain the instantaneous current value of the power factor correction circuit;

[0007] The first overcurrent protection threshold is determined periodically based on the instantaneous current value, and the first overcurrent protection threshold is greater than the instantaneous current value of the corresponding period.

[0008] The power factor correction circuit implements an overcurrent protection strategy based on the first overcurrent protection threshold.

[0009] According to one embodiment of this application, the first overcurrent protection threshold is determined according to the following process:

[0010] Determine the peak value of the instantaneous current within the reference time period;

[0011] The peak current is added to the redundancy value to obtain the first overcurrent protection threshold.

[0012] According to one embodiment of this application, the redundancy value ranges from 2A to 3A.

[0013] According to one embodiment of this application, an overcurrent protection strategy is executed based on a first overcurrent protection threshold, including:

[0014] Obtain the ambient temperature;

[0015] The first overcurrent protection threshold is periodically adjusted based on the ambient temperature to obtain the second overcurrent protection threshold;

[0016] The overcurrent protection strategy is executed based on the second overcurrent protection threshold.

[0017] According to one embodiment of this application, the difference between the second overcurrent protection threshold and the instantaneous current value is negatively correlated with the ambient temperature.

[0018] According to one embodiment of this application, after obtaining the ambient temperature, the method further includes:

[0019] When the ambient temperature is within the target temperature range, perform the step of correcting the first overcurrent protection threshold based on the ambient temperature; or...

[0020] When the ambient temperature is outside the target temperature range, the power factor correction circuit is turned off.

[0021] According to one embodiment of this application, an overcurrent protection strategy is executed based on a second overcurrent protection threshold, including:

[0022] When the instantaneous current value is greater than or equal to the second overcurrent protection threshold, the overcurrent condition is determined to be triggered, and the switching drive signal in the power factor correction circuit is turned off for multiple consecutive cycles.

[0023] When the overcurrent condition is triggered within multiple cycles, the device equipped with a power factor correction circuit is shut down.

[0024] According to one embodiment of this application, the overcurrent protection strategy executed based on a second overcurrent protection threshold further includes:

[0025] When the instantaneous current value is greater than or equal to the second overcurrent protection threshold and greater than or equal to the third overcurrent protection threshold, the power factor correction circuit is turned off. The third overcurrent protection threshold is greater than the second overcurrent protection threshold.

[0026] According to one embodiment of this application, after obtaining the instantaneous current value of the power factor correction circuit, the method further includes:

[0027] If the initial instantaneous current value is less than the preset overcurrent protection threshold, the step of determining the corresponding first overcurrent protection threshold based on the instantaneous current value is executed; or,

[0028] When the instantaneous current value is greater than or equal to the preset overcurrent protection threshold, the power factor correction circuit is turned off.

[0029] Secondly, this application provides an overcurrent protection circuit for a power factor correction circuit, comprising:

[0030] A current sensing circuit is electrically connected to a power factor correction circuit and is configured to detect the instantaneous current value of the power factor correction circuit.

[0031] The driving circuit is electrically connected to the power factor correction circuit and is configured to receive a PWM signal and drive the power factor correction circuit according to the PWM signal.

[0032] The control circuit is electrically connected to the current detection circuit and the drive circuit respectively, and is configured to periodically determine the corresponding first overcurrent protection threshold based on the instantaneous current value, and stop outputting PWM signal to the drive circuit 130 when the instantaneous current value is greater than the first overcurrent threshold.

[0033] According to one embodiment of this application, it also includes:

[0034] Temperature detection unit, configured to detect ambient temperature;

[0035] The control circuit is also electrically connected to the temperature detection unit and is configured to periodically correct the first overcurrent protection threshold according to the ambient temperature to obtain a second overcurrent protection threshold, and stop outputting the PWM signal to the drive circuit when the instantaneous current value is greater than the second overcurrent threshold.

[0036] Thirdly, this application provides a power supply circuit, including a rectifier circuit, a power factor correction circuit, a power module and a load connected in sequence, and the power supply circuit also includes a main control circuit electrically connected to the power factor correction circuit.

[0037] The main control circuit is configured to implement the overcurrent protection method described above, or the main control circuit integrates the overcurrent protection circuit described above.

[0038] Fourthly, this application provides an outdoor unit for an air conditioner, including the power supply circuit described above.

[0039] According to the overcurrent protection method, overcurrent protection circuit power supply circuit, and air conditioner outdoor unit of this application, by generating a corresponding overcurrent protection threshold based on the actual current of the power factor correction circuit, the current connected to the air conditioner outdoor unit has different overcurrent protection thresholds at different current phases, thereby reducing the difference in overcurrent triggering intervals under different phases, improving the reliability of overcurrent protection, and protecting the equipment safety of the air conditioner outdoor unit.

[0040] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0041] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0042] Figure 1 This is one of the flowcharts illustrating the circuit overcurrent protection method provided in the embodiments of this application;

[0043] Figure 2 This is a schematic diagram showing the relationship between the overcurrent protection threshold and the PFC current provided in the embodiments of this application;

[0044] Figure 3 This is a second schematic flowchart of the circuit overcurrent protection method provided in the embodiments of this application;

[0045] Figure 4 This is a schematic diagram of the process for determining the overcurrent protection threshold provided in an embodiment of this application;

[0046] Figure 5 This is the third flowchart illustrating the circuit overcurrent protection method provided in the embodiments of this application;

[0047] Figure 6 This is one of the structural schematic diagrams of the overcurrent protection circuit provided in the embodiments of this application;

[0048] Figure 7 This is the second schematic diagram of the overcurrent protection circuit provided in the embodiments of this application. Detailed Implementation

[0049] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0050] In the following description, a "circuit" refers to a conductive loop consisting of at least one element or sub-circuit connected by an electrical or electromagnetic link. When an element or circuit is said to be "coupled to" or "connected to" another element, or when an element / circuit is said to be "coupled at" or "connected at" two nodes, it can be directly coupled to or connected to the other element, or there may be intermediate elements. The connection between elements can be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there are no intermediate elements between them.

[0051] In the description, the terms "first," "second," etc., are used to distinguish similar objects, not to describe a specific order or sequence. It should be understood that such numerical descriptors can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class, not limited in number; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0052] Furthermore, the use of terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicates that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0053] In related technologies, circuit overcurrent protection has low reliability and is prone to abnormal situations, including failure to identify overcurrent or frequent triggering. This application, through analysis of such phenomena, finds that because the protection threshold is fixed, the difference between the actual current and the protection threshold varies with current changes, resulting in a fluctuating trigger range. When the trigger range is large (i.e., the difference between the actual current and the protection threshold is large), overcurrent protection is less likely to trigger; when the trigger range is small (i.e., the difference between the actual current and the protection threshold is small), overcurrent protection is prone to frequent triggering.

[0054] To address the aforementioned issues, this application proposes an overcurrent protection method, an overcurrent protection circuit power supply circuit, and an outdoor air conditioning unit. By generating a corresponding overcurrent protection threshold based on the actual current of the power factor correction circuit, the current connected to the outdoor air conditioning unit has different overcurrent protection thresholds at different current phases. This reduces the gap between overcurrent triggering intervals at different phases, improves the reliability of overcurrent protection, and protects the equipment safety of the outdoor air conditioning unit.

[0055] Take a PFC (Power Factor Correction) circuit as an example. A PFC circuit is used to improve the power factor of a system. By changing the circuit's input characteristics, it makes the power supply output current more stable, preventing the input power supply from "sinking" or overloading. This type of circuit is widely used in various electronic products that require a large power supply. Of course, the overcurrent protection method, overcurrent protection circuit power supply circuit, and air conditioner outdoor unit proposed in this application can also be applied to other types of circuits, and this application does not impose any limitations on this.

[0056] The current supplied to a PFC circuit is typically AC, therefore the current flowing through it varies with phase. For example, at 0° phase, the instantaneous current flowing through the PFC circuit is 0; at 90° phase, the instantaneous current reaches the peak value of the power supply current. Consequently, if a fixed overcurrent protection threshold is used for overcurrent detection, this threshold is usually slightly higher than the peak power supply current. Therefore, even if an overcurrent occurs at 0° phase, it cannot be detected in advance, and at 90° phase, even a slight current fluctuation may trigger overcurrent protection.

[0057] Reference Figure 1 , Figure 1 A flowchart of an overcurrent protection method for a power factor correction circuit is shown. One embodiment of this application proposes an overcurrent protection method for a power factor correction circuit. This overcurrent protection method includes steps 10, 20, and 30.

[0058] Step 10: Obtain the instantaneous current value of the power factor correction circuit;

[0059] Step 20: Periodically determine the corresponding first overcurrent protection threshold based on the instantaneous current value. The first overcurrent protection threshold is greater than the instantaneous current value of the corresponding period.

[0060] Step 30: Implement an overcurrent protection strategy for the power factor correction circuit based on the first overcurrent protection threshold.

[0061] The PFC circuit has a corresponding main control circuit. The execution subject of the circuit overcurrent protection method proposed in this application can be the main control circuit or the control chip installed inside the main control circuit. Of course, it can also be other circuits with sampling and output control functions. This implementation does not limit this. The following description takes the control chip as the execution subject.

[0062] The control chip can integrate a sampling circuit or have an external sampling circuit. The sampling circuit is electrically connected to the PFC circuit to collect the current flowing through the PFC circuit in real time or periodically at set intervals. The control chip determines the instantaneous current value of the PFC circuit based on the collected data. The sampling circuit can use a resistance sampling principle or a sampling current sensor, etc.

[0063] In this embodiment, a corresponding first overcurrent protection threshold is determined based on the instantaneous current value. By periodically calibrating the first overcurrent protection threshold, the instantaneous current value at different stages of change is compared with different protection thresholds. Specifically, the first overcurrent protection threshold is calibrated multiple times within one complete current change cycle.

[0064] In some embodiments, the first overcurrent protection threshold is determined by the following process: determining the peak current value of the instantaneous current value within a reference time period; adding the peak current value to the redundancy value to obtain the first overcurrent protection threshold.

[0065] The reference time period is shorter than the duration of a complete current change cycle. For example, if the complete current change cycle is 20ms, the reference time period can be 1ms or 2ms, etc. The specific number of times can be set according to requirements. Furthermore, after recording the current peak value within the first reference time period, the control chip can immediately begin recording the next reference time period, or it can start recording the next reference time period after a certain interval.

[0066] In another embodiment, the average value of the instantaneous current over the reference time period can be added to the redundancy value to obtain the first overcurrent protection threshold. Specifically, it can be determined based on the trend of current change within each corresponding reference time period; this embodiment does not impose any limitations on this.

[0067] As an example, the range of redundant values ​​is 2A to 3A.

[0068] Since the changing trend of the first overcurrent protection threshold is the same as the theoretical changing trend of the circuit current, a slightly redundant value can be added to the circuit current to form a more reliable protection threshold. The redundant value can be 2A, 2.5A, or 3A, etc.

[0069] Reference Figure 2 , Figure 2This paper illustrates a correlation between current and threshold. As an example, the current waveform of the PFC circuit can be the absolute value of a sine wave, comprising a rising phase and a falling phase. In related technologies using a fixed threshold, the trigger range is extremely large at 0° phase, easily leading to failure to trigger overcurrent protection in a timely manner; conversely, the trigger range is extremely small at 90° phase, easily leading to frequent overcurrent protection triggers. In this embodiment, the rising and falling phases are further divided into multiple stages. By calibrating the protection threshold at each stage, the difference between the provided protection threshold and the current of the PFC circuit is essentially the same at each phase, effectively detecting overcurrent and reducing the likelihood of failure to trigger or frequent triggering.

[0070] In some embodiments, after obtaining the instantaneous current value of the circuit, the method further includes: when the instantaneous current value obtained for the first time is less than a preset overcurrent protection threshold, performing a step of determining a corresponding first overcurrent protection threshold based on the instantaneous current value; or, when the instantaneous current value is greater than or equal to the preset overcurrent protection threshold, shutting down the circuit.

[0071] The initial instantaneous current value refers to the instantaneous current value of the PFC circuit represented by the first signal received by the control chip from the current detection unit after startup. If the initial instantaneous current value is greater than or equal to the preset overcurrent protection threshold, it indicates that the PFC circuit may be in an overcurrent state. To protect the PFC circuit, it can be shut down, or even the entire outdoor unit of the air conditioner equipped with the PFC circuit can be shut down. If the initial instantaneous current value is less than the preset overcurrent protection threshold, it indicates that the PFC circuit is in a normal state and can continue to operate. The preset overcurrent protection threshold can be determined based on the peak value of the PFC circuit current within a changing cycle. Of course, it can also be set according to requirements, and this implementation does not impose any limitations on this.

[0072] It should be noted that implementing an overcurrent protection strategy for the PFC circuit based on the first overcurrent protection threshold can mean comparing the sampled instantaneous current value with the first overcurrent protection threshold. If the instantaneous current value is greater than or equal to the first overcurrent protection threshold, an overcurrent is determined to have occurred; if the instantaneous current value is less than the first overcurrent protection threshold, no overcurrent is determined to have occurred. Then, the overcurrent protection strategy is executed when an overcurrent occurs.

[0073] Overcurrent protection strategies can be protection programs set inside the control chip, which can include a series of circuit control processes, such as shutting down the overcurrent PFC circuit or shutting down the corresponding whole device. The specific settings can be configured according to requirements, and this implementation method does not limit them.

[0074] Reference Figure 3 , Figure 3A flow chart of an overcurrent protection method for a power factor correction circuit is shown. In some embodiments, step 30 may include steps 31, 32, and 33.

[0075] Step 31: Obtain the ambient temperature;

[0076] Step 32: Periodically adjust the first overcurrent protection threshold according to the ambient temperature to obtain the second overcurrent protection threshold;

[0077] Step 33: Execute the overcurrent protection strategy according to the second overcurrent protection threshold.

[0078] Ambient temperature refers to the temperature of the environment in which the outdoor unit of an air conditioner equipped with a PFC circuit is located. The PFC circuit has an overcurrent protection mechanism to implement overcurrent protection methods. Because the outdoor unit of an air conditioner is located in an outdoor environment, the ambient temperature varies greatly with the seasons, or in some regions, there is a significant difference between day and night temperatures, resulting in a large operating temperature range for the outdoor unit. The current carrying capacity of the outdoor unit also differs at different temperatures, and related technologies do not take temperature into account when specifying overcurrent protection schemes for outdoor units.

[0079] As an example, the control chip can be equipped with a temperature sensor to detect the ambient temperature of the environment where the outdoor unit of the air conditioner is located. The control chip receives the detection data fed back by the temperature sensor to obtain the ambient temperature. Alternatively, the control chip can also be equipped with a query unit that can query local meteorological data via a network to obtain the ambient temperature.

[0080] The modification of the first overcurrent protection threshold includes further increasing or decreasing the first overcurrent protection threshold. When the first overcurrent protection threshold is increased, the difference between the second overcurrent protection threshold and the instantaneous current value (i.e., the triggering interval) is larger; when the first overcurrent protection threshold is decreased, the difference between the second overcurrent protection threshold and the instantaneous current value (i.e., the triggering interval) is smaller.

[0081] It is understandable that the current-carrying capacity of a PFC circuit is affected by temperature to some extent, and temperature may also affect the operating status of the outdoor unit of the air conditioner. Therefore, the overcurrent detection requirements of the PFC circuit differ under different temperatures. The requirements may be more stringent, requiring a smaller trigger range; or more lenient, requiring a larger trigger range. The correspondence between temperature and correction amplitude can be set according to requirements, and this implementation does not impose any restrictions on this. The correction amplitude refers to the increase or decrease in the first overcurrent protection threshold.

[0082] In some embodiments, the period for correcting the first overcurrent protection threshold can be the same as the period for calibrating the first overcurrent protection threshold based on the instantaneous current value. This same period simplifies the process of determining the overcurrent protection threshold.

[0083] In some embodiments, the difference between the second overcurrent protection threshold and the instantaneous current value is negatively correlated with the ambient temperature.

[0084] Generally, the higher the ambient temperature, the more susceptible the PFC circuit is to damage under overcurrent conditions. Therefore, at higher temperatures, reducing the first overcurrent protection threshold and the difference between the second overcurrent protection threshold and the instantaneous current value narrows the overcurrent trigger range, allowing for faster detection of overcurrent situations and ensuring the safety of the outdoor unit in high-temperature environments. Conversely, at low temperatures, appropriately increasing the first overcurrent protection threshold and the difference between the second overcurrent protection threshold and the instantaneous current value expands the overcurrent trigger range, thereby improving the PFC circuit's efficiency. At low temperatures, the second overcurrent protection threshold must ensure that the current in the PFC circuit does not exceed the maximum permissible current.

[0085] As an example, a pre-established correspondence between the correction value for the first overcurrent protection threshold and the ambient temperature can be created. After determining the current ambient temperature, the corresponding correction value is determined by querying this correspondence, and then this correction value is used to adjust the first overcurrent protection threshold. The correction value can be a numerical value representing the current value, and adjusting the first overcurrent protection threshold can be done by adding or subtracting the correction value from the first overcurrent protection threshold. Alternatively, the correction can be a proportional coefficient, and adjusting the first overcurrent protection threshold can be done by multiplying the first overcurrent protection threshold by a proportional coefficient.

[0086] In some embodiments, after obtaining the ambient temperature, the method further includes: when the ambient temperature is within the target temperature range, performing a step of correcting the first overcurrent protection threshold based on the ambient temperature; or, when the ambient temperature is outside the target temperature range, turning off the power factor correction circuit.

[0087] The target temperature range can be defined as the temperature range within which the PFC circuit can operate normally. Taking an air conditioner outdoor unit as an example, the target temperature range can be -25℃ to 60℃. When the current ambient temperature is within the target temperature range, it indicates that the air conditioner outdoor unit can operate normally. Then, the first overcurrent protection threshold is adjusted based on the current ambient temperature, and the overcurrent protection strategy is executed. If the current ambient temperature is outside the target temperature range, it indicates that the PFC circuit is not suitable for operation. To avoid damage to components, the PFC circuit can be shut down, and even the air conditioner outdoor unit can be turned off.

[0088] In this embodiment, a corresponding correction value can be set for the temperature range of -25℃ to 60℃. The relationship between the temperature and the correction value can be linear or non-linear, and can be set according to the requirements. This embodiment does not limit this.

[0089] In some embodiments, the specific process of executing the overcurrent protection strategy according to the second overcurrent protection threshold may include: when the instantaneous current value is greater than or equal to the second overcurrent protection threshold, determining that an overcurrent condition is triggered, and turning off the switch drive signal in the power factor correction circuit for multiple consecutive cycles; when the overcurrent condition is triggered for multiple cycles, controlling the device equipped with the power factor correction circuit to stop.

[0090] In this embodiment, the PFC circuit employs CBC (Cycle-by-Cycle) overcurrent protection, offering high response speed and flexibility. A second overcurrent protection threshold serves as the trigger for CBC overcurrent protection. When the instantaneous current value is greater than or equal to the second overcurrent protection threshold, the PWM signal in the PFC circuit is shut down to suppress current surges. If the current in the PFC circuit remains greater than the second overcurrent protection threshold over multiple cycles, a hardware overcurrent protection is triggered, controlling the outdoor unit of the air conditioner to shut down and reducing the risk of damage.

[0091] The triggering condition for hardware overcurrent can be either multiple consecutive triggers of CBC overcurrent protection or a certain number of triggers of CBC overcurrent protection within multiple consecutive cycles. Specific conditions and trigger counts can be selected according to requirements, and this implementation does not impose any limitations on them.

[0092] In other embodiments, the first overcurrent protection threshold can also be directly used as the threshold for triggering CBC overcurrent protection (i.e., without modification by ambient temperature), and the specific process is the same as that of the second overcurrent protection threshold as the threshold for triggering CBC overcurrent protection.

[0093] In some embodiments, the specific process of executing the overcurrent protection strategy according to the second overcurrent protection threshold may further include: when the instantaneous current value is greater than or equal to the second overcurrent protection threshold and greater than or equal to the third overcurrent protection threshold, the power factor correction circuit is turned off, wherein the third overcurrent protection threshold is greater than the second overcurrent protection threshold.

[0094] In this embodiment, under the CBC overcurrent protection strategy, the second overcurrent protection threshold is a software overcurrent. When the instantaneous current value is greater than or equal to the second overcurrent protection threshold, the PFC circuit is in an overcurrent state, but the entire machine does not stop. If the instantaneous current value is too large, it may cause damage to the entire machine. Therefore, the third overcurrent protection threshold, as a hardware overcurrent threshold, can reduce the risk of damage caused by excessive instantaneous current when the instantaneous current value triggers CBC protection, and when the number of CBC protection triggers has not reached the set number.

[0095] Reference Figure 4 , Figure 4This paper illustrates a process for determining the CBC protection threshold. As an example, after the system starts up, the PFC circuit begins operation, and the PFC current begins sampling. Simultaneously, the ambient temperature sensor can also begin operating, sampling the ambient temperature. When the PFC current exceeds the preset CBC protection threshold, or the ambient temperature exceeds the target temperature range, the PFC circuit is shut down. When the PFC current is less than or equal to the preset CBC protection threshold, and the ambient temperature is within the target temperature range, the determination of the CBC overcurrent protection threshold begins: Firstly, the CBC overcurrent protection threshold is calibrated based on the actual sampled current (i.e., the instantaneous current value), and the PFC current peak value is saved at fixed intervals. If the PFC current peak value changes, the CBC protection threshold is recalibrated; if the PFC current peak value does not change, the saved PFC current peak value is used to obtain the CBC protection threshold. On the other hand, the temperature coefficient for converting the CBC protection threshold based on the ambient temperature is saved at a fixed period. If the temperature coefficient changes, the temperature coefficient is recalculated. If the temperature coefficient does not change, the CBC protection threshold is obtained from the saved temperature coefficient. Finally, the CBC protection threshold calibrated by the PFC current peak and the temperature coefficient are combined to obtain the dynamically adjusted CBC protection threshold.

[0096] Reference Figure 5 , Figure 5 An overcurrent protection process is illustrated. As an example, during system operation, the PFC current is detected and its value is determined to be less than the CBC protection threshold. If the PFC current is less than the CBC protection threshold, the control chip receives a normal PFC operation signal, the IGBT drive signal is unaffected, and the system operates normally. If the PFC current is greater than or equal to the CBC protection threshold, CBC protection is triggered, and the control chip further checks if the PFC current is less than the PFC hardware overcurrent value. If the PFC current is greater than or equal to the PFC hardware overcurrent value, the control chip receives a PFC operation abnormality signal, and the system shuts down. If the PFC current is less than the PFC hardware overcurrent value, the control chip receives a CBC protection signal, shuts down the PWM for several cycles, and the system operates normally, while checking if the number of CBC protection cycles exceeds a set value. If the number of CBC protection cycles exceeds the set value, the control chip receives a PFC operation abnormality signal, and the system shuts down. If the number of CBC protection cycles is less than or equal to the set value during the PWM shutdown period, the control chip determines that PFC has returned to normal, and the system operates normally.

[0097] In the above example, the CBC protection threshold can be either the first overcurrent protection threshold or the second overcurrent protection threshold, and the PFC hardware overcurrent value can be either the third overcurrent protection threshold.

[0098] Reference Figure 6 , Figure 6The structure of an overcurrent protection circuit is shown. An embodiment of this application also proposes an overcurrent protection circuit for a power factor correction circuit 200. In this embodiment, the overcurrent protection circuit includes a current detection circuit 110, a control circuit 120, and a drive circuit 130. The current detection circuit 110 is electrically connected to the power factor correction circuit 200 and configured to detect the instantaneous current value of the power factor correction circuit 200. The drive circuit 130 is electrically connected to the power factor correction circuit 200 and configured to receive a PWM signal and drive the power factor correction circuit 200 according to the PWM signal. The control circuit 120 is electrically connected to both the current detection circuit 110 and the drive circuit 130, and configured to periodically determine a corresponding first overcurrent protection threshold based on the instantaneous current value, and stop outputting the PWM signal to the drive circuit 130 when the instantaneous current value is greater than the first overcurrent threshold. The first overcurrent protection threshold is greater than the instantaneous current value of the corresponding period.

[0099] In this embodiment, the control circuit 120 periodically calibrates the first overcurrent protection threshold based on the instantaneous current value fed back by the current detection circuit 110, thereby comparing the instantaneous current value at different stages of change with different protection thresholds. Specifically, the first overcurrent protection threshold is calibrated multiple times within one complete current change cycle.

[0100] In some embodiments, the control circuit 120 can determine the peak value of the instantaneous current within a reference time period; add the peak current value to the redundancy value to obtain a first overcurrent protection threshold. The reference time period is shorter than the duration of a complete current change cycle. For example, if the complete current change cycle is 20ms, the reference time period can be 1ms or 2ms, etc. The specific number of times can be set according to requirements. The redundancy value ranges from 2A to 3A.

[0101] In this embodiment, when overcurrent protection is triggered by the first overcurrent protection threshold, the control circuit 120 stops outputting the PWM signal. At this time, the PWM signal is inactive to prevent a sudden increase in current. If the instantaneous current value in the PFC circuit remains greater than the first overcurrent threshold after the PWM signal output is stopped, the control circuit 120 executes a shutdown strategy. In this embodiment, the control circuit 120 can employ CBC overcurrent protection, and the first overcurrent protection threshold can be used as the CBC protection threshold.

[0102] In some embodiments, the control circuit 120 may further execute the step of determining the corresponding first overcurrent protection threshold based on the instantaneous current value when the instantaneous current value obtained for the first time is less than the preset overcurrent protection threshold; or, execute a shutdown strategy when the instantaneous current value is greater than or equal to the preset overcurrent protection threshold.

[0103] If the instantaneous current value obtained for the first time is greater than or equal to the preset overcurrent protection threshold, it indicates that the PFC circuit may be in an overcurrent state and a shutdown strategy can be executed to avoid circuit damage.

[0104] It should be noted that the control circuit 120 can implement the circuit overcurrent protection method mentioned in the foregoing embodiments, and it also has the corresponding technical effects, which will not be elaborated here.

[0105] Reference Figure 7 , Figure 7 The structure of an overcurrent protection circuit is shown. In this embodiment, the input side of the PFC circuit is electrically connected to the AC input via a rectifier circuit, and the output side of the PFC circuit is electrically connected to the load via a power module. The control circuit 120 includes an MCU (Microcontroller Unit).

[0106] The current sensing circuit 110 samples the current through resistor R and feeds the sampled signal back to the MCU through an operational amplifier. The MCU determines the instantaneous current value based on the received signal and calibrates the overcurrent protection threshold accordingly, while also performing an overcurrent judgment. If the MCU determines that the instantaneous current value is greater than the overcurrent protection threshold, it generates an overcurrent signal, controlling the drive circuit 130 to stop the output of PWM for several cycles. If the CBC protection is repeatedly triggered a certain number of times within a certain period, the shutdown protection will be directly triggered.

[0107] In some embodiments, the drive circuit 130 can also output an FO signal to the MCU when the PFC current is greater than the hardware overcurrent value. When the MCU receives the FO signal, it triggers a shutdown protection.

[0108] In some embodiments, the overcurrent protection circuit may further include a temperature detection unit 140, which is configured to detect the ambient temperature; the control circuit 120 is also electrically connected to the temperature detection unit 140 and is configured to periodically correct the first overcurrent protection threshold according to the ambient temperature to obtain a second overcurrent protection threshold, and stop outputting the PWM signal to the drive circuit when the instantaneous current value is greater than the second overcurrent threshold.

[0109] Temperature sensor 140 may include a temperature sensor that can be mounted on the device body to detect the temperature of the environment in which the device is located. The MCU receives the detection data fed back by the temperature sensor to obtain the ambient temperature.

[0110] The MCU can adjust the first overcurrent protection threshold based on temperature. For example, it can further increase or decrease the first overcurrent protection threshold to meet the overcurrent detection requirements of the PFC circuit at different temperatures.

[0111] As an example, the difference between the second overcurrent protection threshold and the instantaneous current value is negatively correlated with the ambient temperature. In high-temperature environments, reducing the first overcurrent protection threshold narrows the overcurrent trigger range, allowing for faster detection of overcurrent and ensuring the safety of the outdoor unit. In low-temperature environments, increasing the first overcurrent protection threshold expands the overcurrent trigger range, improving the efficiency of the PFC circuit.

[0112] In some embodiments, the MCU may also perform a step of correcting the first overcurrent protection threshold based on the ambient temperature when the ambient temperature is within the target temperature range; or, when the ambient temperature is outside the target temperature range, shut down the power factor correction circuit. When the current ambient temperature is outside the target temperature range, it indicates that the PFC circuit is currently unsuitable for operation, and a shutdown strategy is executed to avoid device damage.

[0113] One embodiment of this application also provides a power supply circuit. The power supply circuit includes a rectifier circuit, a power factor correction circuit, a power module, and a load connected in sequence. The power supply circuit also includes a main control circuit electrically connected to the power factor correction circuit. The main control circuit is configured to implement the overcurrent protection method described above, or the main control circuit integrates the overcurrent protection circuit described above.

[0114] One possible structure for a power supply circuit can be referenced. Figure 7 The main control circuit may include Figure 7 The MCU in the system. The load varies depending on the device type; for example, it could be a motor or a compressor. The specific structure and principle of the overcurrent protection method and circuit can be found in the foregoing embodiments and will not be repeated here.

[0115] One embodiment of this application also provides an outdoor unit for an air conditioner, which includes the power supply circuit described above. The specific structure and principle of the power supply circuit can be referred to the foregoing embodiments, and will not be repeated here.

[0116] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0117] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

[0118] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A method of overcurrent protection for a power factor correction circuit, comprising: The method comprises: acquiring an instantaneous current value of the power factor correction circuit; periodically determining a corresponding first over-current protection threshold according to the instantaneous current value, the first over-current protection threshold being greater than the instantaneous current value of the corresponding period; performing an over-current protection strategy on the power factor correction circuit according to the first over-current protection threshold.

2. The overcurrent protection method of claim 1, wherein, The first over-current protection threshold is determined according to the following process: determining a current peak value of the instantaneous current value in a reference time period; adding the current peak value to a redundancy value to obtain a first over-current protection threshold.

3. The overcurrent protection method of claim 2, wherein, The redundancy value ranges from 2A to 3A.

4. The overcurrent protection method according to any one of claims 1 to 3, characterized in that, The over-current protection strategy according to the first over-current protection threshold comprises: acquiring an ambient temperature; periodically correcting the first over-current protection threshold according to the ambient temperature to obtain a second over-current protection threshold; performing an over-current protection strategy according to the second over-current protection threshold.

5. The overcurrent protection method of claim 4, wherein, The difference between the second over-current protection threshold and the instantaneous current value is negatively correlated with the ambient temperature.

6. The overcurrent protection method of claim 4, wherein, After acquiring the ambient temperature, the method further comprises: when the ambient temperature is within a target temperature range, performing the step of correcting the first over-current protection threshold according to the ambient temperature; or when the ambient temperature is outside the target temperature range, shutting down the power factor correction circuit.

7. The overcurrent protection method of claim 4, wherein, The over-current protection strategy according to the second over-current protection threshold comprises: when the instantaneous current value is greater than or equal to the second over-current protection threshold, determining that an over-current condition is triggered, and shutting down a switch driving signal in the power factor correction circuit for a plurality of continuous periods; when the over-current condition is triggered for a plurality of periods, controlling a device provided with the power factor correction circuit to shut down.

8. The overcurrent protection method of claim 7, wherein, The over-current protection strategy according to the second over-current protection threshold further comprises: when the instantaneous current value is greater than or equal to the second over-current protection threshold and greater than or equal to a third over-current protection threshold, shutting down the power factor correction circuit, the third over-current protection threshold being greater than the second over-current protection threshold.

9. The overcurrent protection method of any one of claims 1-3, wherein, After acquiring the instantaneous current value of the power factor correction circuit, the method further comprises: when the first-acquired instantaneous current value is less than a preset over-current protection threshold, performing the step of determining a corresponding first over-current protection threshold according to the instantaneous current value; or when the instantaneous current value is greater than or equal to the preset over-current protection threshold, shutting down the power factor correction circuit.

10. An overcurrent protection circuit for a power factor correction circuit, characterized by The method comprises: a current detection circuit electrically connected to a power factor correction circuit and configured to detect an instantaneous current value of the power factor correction circuit; a driving circuit electrically connected to the power factor correction circuit and configured to access a PWM signal and drive the power factor correction circuit according to the PWM signal; a control circuit electrically connected to the current detection circuit and the driving circuit and configured to periodically determine a corresponding first over-current protection threshold according to the instantaneous current value and stop outputting the PWM signal to the driving circuit when the instantaneous current value is greater than the first over-current threshold.

11. The overcurrent protection circuit of claim 10, wherein, The method further comprises: a temperature detection unit configured to detect an ambient temperature; The control circuit is also electrically connected with the temperature detection unit, and is configured to periodically correct the first over-current protection threshold according to the ambient temperature, obtain a second over-current protection threshold, and stop outputting the PWM signal to the drive circuit when the instantaneous current value is greater than the second over-current threshold.

12. A power supply circuit, characterized by comprising: The power supply circuit comprises, in sequence, a rectifier circuit, a power factor correction circuit, a power module and a load, and further comprises a master control circuit electrically connected with the power factor correction circuit. The master control circuit is configured to implement the over-current protection method according to any one of claims 1-9, or the master control circuit is integrated with the over-current protection circuit according to claim 10 or 11.

13. An air conditioner outdoor unit characterized by comprising: The power supply circuit comprises the power supply circuit according to claim 12.

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