Totem Pole Off-Grid Inverter Circuit and its Critical Current Mode Control Method

Abstract

This application discloses a totem-pole off-grid inverter circuit and its critical current mode control method. The critical current mode control method for the totem-pole off-grid inverter circuit includes: determining a peak current; acquiring an output current, comparing the output current with the peak current to obtain a first comparison branch output signal, and comparing the output current with zero to obtain a second comparison branch output signal; triggering a target output signal based on the first and second comparison branch output signals; and turning the controlled object on or off according to the direction of the peak current and the target output signal, or maintaining the current control state of the controlled object, so that the totem-pole off-grid inverter circuit operates in critical current mode. This critical current mode control method for the totem-pole off-grid inverter circuit enables the totem-pole off-grid inverter circuit to automatically adjust and control its operation in critical current mode, effectively reducing EMC interference.

Description

Technical Field

[0001] This application relates to the field of electronic circuit technology, and in particular to a totem pole off-grid inverter circuit and its critical current mode control method. Background Technology

[0002] Current totem pole off-grid inverter circuits generally use continuous current mode (CCM), which has significant EMC (Electromagnetic Compatibility) interference. Summary of the Invention

[0003] In view of this, embodiments of this application provide a totem pole off-grid inverter circuit and its critical current mode control method to solve the problem of large EMC interference in continuous current mode.

[0004] In a first aspect, embodiments of this application provide a critical current-mode control method for a totem-pole off-grid inverter circuit, comprising:

[0005] Determine the peak current, wherein the peak current includes the positive direction or the negative direction. When the peak current is in the positive direction, the first switch is the controlled object. When the peak current is in the negative direction, the second switch is the controlled object. The first switch and the second switch form a half-bridge structure.

[0006] The output current is acquired, and the output current is compared with the peak current to obtain a first comparison branch output signal. The output current is also compared with zero to obtain a second comparison branch output signal.

[0007] The target output signal is triggered based on the first comparison branch output signal and the second comparison branch output signal;

[0008] The control object is turned on or off according to the direction of the peak current and the target output signal, or the current control state of the control object is maintained, so that the totem pole off-grid inverter circuit operates in the critical current mode. In the same direction of the peak current, when the absolute value of the output current is greater than the absolute value of the peak current, the control object is turned off; when the absolute value of the output current is not greater than the absolute value of the peak current and is greater than the zero value, the control object maintains the current control state; when the output current is equal to the zero value, the direction of the peak current changes and the control object is turned on.

[0009] In addition to the aspects described above and any possible implementations, a further implementation is provided in which the determination of the peak current includes:

[0010] Obtain the output voltage setting command, and determine the reference output voltage according to the output voltage setting command;

[0011] The output voltage is acquired and input into a voltage loop, wherein the voltage loop includes a loop controller;

[0012] The output voltage is compared with the reference output voltage to obtain the voltage difference;

[0013] The voltage difference is input into the loop controller to obtain the loop controller output;

[0014] The peak current is determined based on the output of the loop controller.

[0015] In addition to the aspects and any possible implementations described above, a further implementation is provided, wherein comparing the output current with the peak current to obtain a first comparison branch output signal, and comparing the output current with zero to obtain a second comparison branch output signal, includes:

[0016] The output current is input to a first comparator and a second comparator for comparison to obtain a first comparison branch output signal and a second comparison branch output signal, wherein the value used by the first comparator for comparison is the peak current, and the value used by the second comparator for comparison is the zero value;

[0017] When the output current is greater than the peak current, the first comparison branch output signal is a high-level signal; when the output current is not greater than the peak current, the first comparison branch output signal is a low-level signal.

[0018] When the output current is greater than the zero value, the second comparison branch output signal is a high-level signal; when the output current is not greater than the zero value, the second comparison branch output signal is a low-level signal.

[0019] In addition to the aspects described above and any possible implementation, a further implementation is provided in which the first comparator has an NOT gate on the path of the peak current in the negative direction, the second comparator has an NOT gate on the path of the peak current in the positive direction, and the target output signal is triggered by an RS flip-flop.

[0020] In addition to the aspects described above and any possible implementations, a further implementation is provided, wherein triggering the target output signal based on the first comparison branch output signal and the second comparison branch output signal includes:

[0021] Based on the direction of the peak current, the first comparison branch output signal, and the second comparison branch output signal, a first condition signal and a second condition signal are obtained.

[0022] The first condition signal and the second condition signal are input into the RS flip-flop to trigger the target output signal.

[0023] As described above and in any possible implementation, a further implementation is provided, which further includes, before inputting the first condition signal and the second condition signal into the RS flip-flop to trigger the target output signal:

[0024] The number of times the second condition signal is output is counted. When the number of outputs reaches a threshold, the second condition signal triggers an output condition, and the count value is cleared to zero.

[0025] In addition to the aspects and any possible implementations described above, a further implementation is provided, wherein the method further includes:

[0026] Determine the output voltage;

[0027] The fourth switch is turned on when the output voltage is greater than zero.

[0028] When the output voltage is less than zero, the third switch is turned on. The third and fourth switches form a half-bridge structure, and the first, second, third, and fourth switches form a full-bridge structure. The first and fourth switches are diagonally opposite each other.

[0029] Secondly, embodiments of this application also provide a totem pole off-grid inverter circuit, comprising:

[0030] The system comprises a voltage source, a full-bridge structure, an output inductor, and a load resistor. The full-bridge structure includes a first switch, a second switch, a third switch, and a fourth switch, wherein the first switch and the fourth switch are diagonally opposite each other.

[0031] A peak current determination module is used to determine a peak current, wherein the peak current includes a positive direction or a negative direction. When the peak current is in the positive direction, the first switch is the controlled object, and when the peak current is in the negative direction, the second switch is the controlled object. The first switch and the second switch are a half-bridge structure.

[0032] The target output signal triggering module is used to acquire the output current, compare the output current with the peak current to obtain a first comparison branch output signal, and compare the output current with zero value to obtain a second comparison branch output signal, and trigger the target output signal according to the first comparison branch output signal and the second comparison branch output signal;

[0033] A pulse output module is used to turn the controlled object on or off according to the direction of the peak current and the target output signal, or to maintain the current control state of the controlled object, so that the totem pole off-grid inverter circuit operates in the critical current mode. Specifically, in the same direction of the peak current, when the absolute value of the output current is greater than the absolute value of the peak current, the controlled object is turned off; when the absolute value of the output current is not greater than the absolute value of the peak current but is greater than zero, the controlled object maintains its current control state; when the output current equals zero, the direction of the peak current changes, and the controlled object is turned on.

[0034] Furthermore, the target output signal triggering module is also used for:

[0035] Obtain the output voltage;

[0036] When the output voltage is greater than zero, the fourth switch is turned on;

[0037] When the output voltage is less than zero, the third switch is turned on, wherein the third switch and the fourth switch constitute the half-bridge structure.

[0038] Furthermore, the target output signal triggering module includes a first comparator and a second comparator;

[0039] The first comparator has an NOT gate on the path of the peak current in the negative direction, and the second comparator has an NOT gate on the path of the peak current in the positive direction.

[0040] A counter is used to count the number of times the second condition signal is output. When the number of outputs reaches a threshold, the second condition signal triggers an output condition, and the count value of the counter is cleared to zero. The second condition signal is obtained based on the direction of the peak current and the second comparison branch output signal.

[0041] An RS flip-flop is configured to receive the second condition signal and the first condition signal, and output a target output signal, wherein the first condition signal is obtained based on the direction of the peak current and the first comparison branch output signal.

[0042] Furthermore, the peak current determination module is also used for:

[0043] Obtain the output voltage setting command, and determine the reference output voltage according to the output voltage setting command;

[0044] The output voltage is acquired and input into a voltage loop, wherein the voltage loop includes a loop controller;

[0045] The output voltage is compared with the reference output voltage to obtain the voltage difference;

[0046] The voltage difference is input into the loop controller to obtain the loop controller output;

[0047] The peak current is determined based on the output of the loop controller.

[0048] Furthermore, the target output signal triggering module is also used for:

[0049] The output current is input to a first comparator and a second comparator for comparison to obtain a first comparison branch output signal and a second comparison branch output signal, wherein the value used by the first comparator for comparison is the peak current, and the value used by the second comparator for comparison is the zero value;

[0050] When the output current is greater than the peak current, the first comparison branch output signal is a high-level signal; when the output current is not greater than the peak current, the first comparison branch output signal is a low-level signal.

[0051] When the output current is greater than the zero value, the second comparison branch output signal is a high-level signal; when the output current is not greater than the zero value, the second comparison branch output signal is a low-level signal.

[0052] In this embodiment, peak current is used to control the totem-pole off-grid inverter circuit in a critical current mode. Specifically, the switching transistor to be controlled is first determined by the direction of the peak current. Then, based on the output current, the first comparison branch output signal and the second comparison branch output signal are obtained by comparing the peak current with a zero value. A target output signal is then triggered. Based on the target output signal and the direction of the peak current, the corresponding switching transistor is turned on, turned off, kept on, or kept off, thereby controlling the totem-pole off-grid inverter circuit in a critical current mode. This application enables the totem-pole off-grid inverter circuit to automatically adjust and control its operation in a critical current mode, effectively reducing EMC interference. Furthermore, since this application uses a zero-voltage turn-on switching transistor, the cost of the switching transistor can be reduced. Moreover, this application uses peak current control, which greatly enhances the current control capability and avoids the problem of excessive stress on the switching transistor due to excessive current. Attached Figure Description

[0053] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0054] Figure 1 This is a schematic diagram of the structure of a totem pole off-grid inverter circuit in an embodiment of this application;

[0055] Figure 2 This is a logic circuit diagram of a totem pole off-grid inverter circuit that uses peak current to operate in critical current mode in an embodiment of this application.

[0056] Figure 3 This is a voltage loop control diagram of a totem pole off-grid inverter circuit in an embodiment of this application. Detailed Implementation

[0057] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0058] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0059] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0060] It should be understood that the term "and / or" used in this document is merely a description of the same field in the related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0061] It should be understood that although terms such as first, second, third, etc., may be used to describe preset ranges in the embodiments of this application, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from one another. For example, without departing from the scope of the embodiments of this application, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0062] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0063] In totem-pole off-grid inverter circuits, a totem pole refers to a half-bridge structure, utilizing one or more totem poles to achieve current inversion. Inversion refers to the process of converting direct current (DC) to alternating current (AC). Off-grid inverter circuits are circuit systems disconnected from the public power grid, making them suitable for areas without grid coverage, such as deserts, plateaus, and forests, ensuring a constant supply of electricity. In practical applications, totem-pole off-grid inverters generally employ continuous current mode (CDM). This CDM is simple to implement and easy to control, but it suffers from significant EMC interference and high losses in the switching transistors. At higher switching frequencies, high-frequency transistors are required, increasing costs. Boundary Current Mode (BCM) can effectively address these issues, but currently, accurate, stable, and easily implemented control methods are lacking for totem-pole off-grid inverter circuits.

[0064] Therefore, this application proposes a critical current-mode control method for a totem-pole off-grid inverter circuit using peak current. This critical current-mode control method for the totem-pole off-grid inverter circuit includes:

[0065] S1: Determine the peak current, where the peak current includes the positive or negative direction. When the peak current is in the positive direction, the first switch is the controlled object. When the peak current is in the negative direction, the second switch is the controlled object. The first and second switches form a half-bridge structure.

[0066] In one embodiment, the direction of the peak current determines the controlled object. For example, when the peak current is in the positive direction, the circuit controls the first switch, while the second switch is not controlled; conversely, when the peak current is in the negative direction, the circuit controls the second switch, while the first switch is not operated. This application binds the direction of the peak current to the controlled object, which firstly aligns with the change in current direction during the DC-to-AC conversion of the inverter circuit, and secondly, it can utilize the change in the direction of the peak current to determine the zero point of the critical current mode, thereby achieving more precise control of the critical current mode.

[0067] S2: Acquire the output current, compare the output current with the peak current to obtain the first comparison branch output signal, and compare the output current with zero value to obtain the second comparison branch output signal.

[0068] In critical current mode, the peak current point and the zero point reflect the characteristics of this mode. In one embodiment, based on the characteristics of critical current mode, the acquired output current is compared with the peak current and the zero point respectively, and the specific state of the current circuit is determined according to the comparison results. Specifically, when the absolute value of the output current exceeds the absolute value of the peak current, it indicates that the current state has exceeded the peak critical point in critical current mode and needs to be adjusted immediately. By comparing the output current and the zero point, the switching time of the switching transistor can be determined. At the zero point, the current direction of the output current is automatically changed, thereby achieving the effect of inversion. Secondly, the zero point of critical current mode can also be determined, so that the circuit is controlled in critical current mode.

[0069] S3: Trigger the target output signal based on the first comparison branch output signal and the second comparison branch output signal.

[0070] In one embodiment, the first and second comparison branch output signals are intermediate results after comparison. To ultimately achieve the critical current mode control effect, these two signals need to be converted to trigger the target output signal. This target output signal is the control signal desired by the user, which determines the control of the controlled object, ensuring that the totem-pole off-grid inverter circuit can operate accurately and stably in critical current mode. For example, the first comparison branch output signal is output by a first comparator, and the second comparison branch output signal is output by a second comparator. The signals output by these two comparators will be converted through a device such as an RS flip-flop to obtain the final target output signal.

[0071] S4: Based on the direction of the peak current and the target output signal, the control object is turned on or off, or the current control state of the control object is maintained, so that the totem pole off-grid inverter circuit operates in critical current mode. Specifically, in the same peak current direction, when the absolute value of the output current is greater than the absolute value of the peak current, the control object is turned off; when the absolute value of the output current is not greater than the absolute value of the peak current and is greater than zero, the control object maintains its current control state; when the output current is equal to zero, the direction of the peak current changes, and the control object is turned on.

[0072] Understandably, the direction of the peak current determines the controlled object, which continuously switches within the critical current mode, while the control corresponding to the target output signal (such as on / off) remains fixed. In this embodiment, the direction of the peak current is used to control different controlled objects. Furthermore, the state of the totem-pole off-grid inverter circuit is determined by comparing the absolute value of the output current with the absolute value of the peak current, allowing the circuit to control the current within the critical current mode after numerical comparison. For example, within the same peak current direction, if the absolute value of the output current is greater than the absolute value of the peak current, it indicates that the output current exceeds the range of the critical current mode. In this case, the controlled object should be turned off, and the circuit output current will decrease until it reaches zero, completing the process of the critical current mode transitioning from the peak point to zero. Then, at the zero-point state, the direction of the peak current is changed, and the modified controlled object is turned on to achieve the effect of critical value transition in the critical current mode. Afterward, preparations are made to increase the output current, completing the process of the critical current mode transitioning from zero to the peak point again. When the absolute value of the output current is not greater than the absolute value of the peak current and is greater than zero, the controlled object maintains its current control state (if the controlled object is in the on state, it will remain in the on state; if the controlled object is in the off state, it will remain in the off state).

[0073] Furthermore, the step of determining the peak current also includes:

[0074] 1-1: Obtain the output voltage setting command and determine the reference output voltage based on the output voltage setting command.

[0075] 1-2: Obtain the output voltage and input the output voltage into the voltage loop, wherein the voltage loop includes a loop controller.

[0076] 1-3: Compare the output voltage with the reference output voltage to obtain the voltage difference.

[0077] 1-4: Input the voltage difference into the loop controller to obtain the loop controller output.

[0078] 1-5: Determine the peak current based on the output of the loop controller.

[0079] In one embodiment, the specific peak value of the peak current can be controlled by the user. Understandably, based on the characteristics of the critical current mode, the peak current is twice the average current. The peak current can be obtained from the average current, which can be determined by the output voltage. Specifically, the user can issue an output voltage setting command through a host computer, compare the reference output voltage with the actual output voltage of the current to obtain the voltage difference, and then input the voltage difference into a loop controller (e.g., a PI controller) to obtain the loop controller output. Based on this loop control output, the output voltage of the current is adjusted so that the output voltage approximates the reference output voltage. This reference output voltage is the output voltage desired by the user. When the output voltage of the current approximates the reference output voltage, the peak current of the circuit will reach the user's desired magnitude.

[0080] Furthermore, comparing the output current with the peak current to obtain the first comparison branch output signal, and comparing the output current with zero to obtain the second comparison branch output signal, includes:

[0081] 2-1: The output current is input to the first comparator and the second comparator for comparison to obtain the first comparison branch output signal and the second comparison branch output signal. The value used by the first comparator to compare is the peak current, and the value used by the second comparator to compare is zero.

[0082] 2-2: When the output current is greater than the peak current, the output signal of the first comparison branch is a high-level signal; when the output current is not greater than the peak current, the output signal of the first comparison branch is a low-level signal.

[0083] 2-3: When the output current is greater than zero, the output signal of the second comparison branch is a high-level signal; when the output current is not greater than zero, the output signal of the second comparison branch is a low-level signal.

[0084] In one embodiment, in the specific logic circuit design, the comparison between the output current, peak current, and zero value is achieved through two comparators. The output of the comparators is either 0 or 1, meaning that the output signals of the first and second comparison branches only have two possibilities: a high level or a low level. In this application, the structure of this comparator can effectively simplify the circuit, and the current circuit current status can be determined through the signal output by the comparator, thus providing a technical basis for implementing the critical current mode based on the current circuit current status.

[0085] Furthermore, the first comparator has an NOT gate on the path of the peak current in the negative direction, the second comparator has an NOT gate on the path of the peak current in the positive direction, and the target output signal is triggered by an RS flip-flop.

[0086] It should be noted that peak current includes both positive and negative directions. The path of peak current in the negative direction refers to the transmission path of the electrical signal when the peak current direction is negative, and the path of peak current in the positive direction refers to the transmission path of the electrical signal when the peak current direction is positive. The inclusion of a NOT gate on the negative peak current path of the first comparator means that a NOT gate is placed after the first comparator on the transmission path of the electrical signal when the peak current is in the negative direction. This NOT gate is used to perform a NOT operation on the electrical signal output by the first comparator. Similarly, the inclusion of a NOT gate on the positive peak current path of the second comparator means that a NOT gate is placed after the second comparator on the transmission path of the electrical signal when the peak current is in the positive direction. This NOT gate is used to perform a NOT operation on the electrical signal output by the second comparator.

[0087] Further, the step of triggering the target output signal based on the first comparison branch output signal and the second comparison branch output signal includes:

[0088] 3-1: Based on the direction of the peak current, the first comparison branch output signal, and the second comparison branch output signal, the first condition signal and the second condition signal are obtained.

[0089] 3-2: Input the first condition signal and the second condition signal into the RS flip-flop to trigger the target output signal.

[0090] In one embodiment, the target output signal can be triggered by different flip-flops, provided that the first comparator output signal and the second comparator output signal are converted into accurate control of the switching transistor to achieve critical current mode control. Specifically, an RS flip-flop is one feasible solution. When an RS flip-flop is used, the first comparator needs to have an NOT gate on the path of the peak current in the negative direction, and the second comparator needs to have an NOT gate on the path of the peak current in the positive direction. In this way, by converting the signal from 0 to 1 or from 1 to 0, the first condition signal and the second condition signal input to the RS flip-flop can be adjusted, so that the target output signal triggered by the RS flip-flop can control the switching transistor (the direction of the peak current determines whether it controls the first or second switching transistor), allowing the totem-pole off-grid inverter circuit to operate in critical current mode.

[0091] Furthermore, the method also includes: counting the number of times the second condition signal is output; when the number of outputs reaches a threshold, the second condition signal triggers an output condition and the count value is cleared to zero.

[0092] In one embodiment, a condition for issuing the second condition signal can also be set. Specifically, a counter can be set on the path of the second condition signal. The second condition signal is only allowed to be issued when the counter reaches a threshold number of times. This counter can effectively control frequency changes, limiting the frequency of the switching transistor to a desired range, and thus protecting the switching losses of the switching transistor.

[0093] Furthermore, the method also includes:

[0094] The output voltage is determined. When the output voltage is greater than zero, the fourth switch is turned on; when the output voltage is less than zero, the third switch is turned on. The third and fourth switches form a half-bridge structure, while the first, second, third, and fourth switches form a full-bridge structure. The first and fourth switches are diagonally opposite each other.

[0095] In one embodiment, the totem poles of this application can specifically be two, with the third and fourth switches forming a full-bridge structure together with the first and second switches. In this application, the on / off states of the third and fourth switches can also be set according to the output voltage. When the output voltage is greater than zero, the fourth switch is on. When the output voltage is less than zero, the third switch is on. In this way, corresponding to the change in the direction of the peak current, the correct on / off states of the third and fourth switches can be controlled, allowing only one switch to be on per switching cycle in a critical current mode, thus reducing the shoot-through risk of the two bridge arm switches.

[0096] In this embodiment, peak current is used to control the totem-pole off-grid inverter circuit in a critical current mode. Specifically, the switching transistor to be controlled is first determined by the direction of the peak current. Then, based on the output current, the first comparison branch output signal and the second comparison branch output signal are obtained by comparing the peak current with a zero value. A target output signal is then triggered. Based on the target output signal and the direction of the peak current, the corresponding switching transistor is turned on, turned off, kept on, or kept off, thereby controlling the totem-pole off-grid inverter circuit in a critical current mode. This application enables the totem-pole off-grid inverter circuit to automatically adjust and control its operation in a critical current mode, effectively reducing EMC interference. Furthermore, since this application uses a zero-voltage turn-on switching transistor, the cost of the switching transistor can be reduced; and since this application uses peak current control, the current control capability is greatly enhanced, avoiding the problem of excessive stress on the switching transistor due to excessive current.

[0097] This application also provides a totem pole off-grid inverter circuit, including:

[0098] The voltage source, full-bridge structure, output inductor and load resistor, wherein the full-bridge structure includes a first switch, a second switch, a third switch and a fourth switch, with the first switch and the fourth switch being diagonally related;

[0099] The peak current determination module is used to determine the peak current, which includes the positive or negative direction. When the peak current is in the positive direction, the first switch is the controlled object, and when the peak current is in the negative direction, the second switch is the controlled object. The first and second switches form a half-bridge structure.

[0100] The target output signal trigger module is used to acquire the output current, compare the output current with the peak current to obtain the first comparison branch output signal, and compare the output current with zero value to obtain the second comparison branch output signal, and trigger the target output signal according to the first comparison branch output signal and the second comparison branch output signal;

[0101] The pulse output module is used to turn the controlled object on or off according to the direction of the peak current and the target output signal, or to maintain the current control state of the controlled object, so that the totem pole off-grid inverter circuit operates in critical current mode. Specifically, in the same peak current direction, when the absolute value of the output current is greater than the absolute value of the peak current, the controlled object is turned off; when the absolute value of the output current is not greater than the absolute value of the peak current and is greater than zero, the controlled object maintains its current control state; when the output current is equal to zero, the direction of the peak current changes and the controlled object is turned on.

[0102] Furthermore, the target output signal triggering module is also used for:

[0103] Obtain the output voltage;

[0104] When the output voltage is greater than zero, the fourth switch is turned on;

[0105] When the output voltage is less than zero, the third switch is turned on. The third and fourth switches form a half-bridge structure.

[0106] Furthermore, the target output signal triggering module includes a first comparator and a second comparator;

[0107] The first comparator has an NOT gate on the path of the peak current in the negative direction, and the second comparator has an NOT gate on the path of the peak current in the positive direction.

[0108] The counter is used to count the number of times the second condition signal is output. When the number of outputs reaches the threshold, the second condition signal triggers the output condition, and the counter value is cleared to zero. The second condition signal is obtained based on the direction of the peak current and the output signal of the second comparison branch.

[0109] An RS flip-flop is used to receive a second condition signal and a first condition signal, and output a target output signal, wherein the first condition signal is obtained based on the direction of the peak current and the first comparison branch output signal.

[0110] Furthermore, the peak current determination module is also used for:

[0111] Obtain the output voltage setting command and determine the reference output voltage based on the output voltage setting command;

[0112] The output voltage is acquired and input into the voltage loop, wherein the voltage loop includes a loop controller;

[0113] The output voltage is compared with the reference output voltage to obtain the voltage difference;

[0114] The voltage difference is input into the loop controller to obtain the loop controller output;

[0115] The peak current is determined based on the output of the loop controller.

[0116] Furthermore, the target output signal triggering module is also used for:

[0117] The output current is input to the first comparator and the second comparator for comparison to obtain the first comparison branch output signal and the second comparison branch output signal. The value used by the first comparator to compare is the peak current, and the value used by the second comparator to compare is zero.

[0118] When the output current is greater than the peak current, the first comparison branch output signal is a high-level signal; when the output current is not greater than the peak current, the first comparison branch output signal is a low-level signal.

[0119] When the output current is greater than zero, the output signal of the second comparison branch is a high-level signal; when the output current is not greater than zero, the output signal of the second comparison branch is a low-level signal.

[0120] Figure 1 This is a schematic diagram of a totem pole off-grid inverter circuit according to an embodiment of this application. Figure 1As shown, this totem-pole off-grid inverter circuit includes a voltage source, a full-bridge structure, an inductor current IL, and an output voltage Uo. The full-bridge structure includes four switching transistors: the first transistor outputs a PWM (Pulse Width Modulation) A signal, the second transistor outputs a PWMB signal, the third transistor outputs a PWMC signal, and the fourth transistor outputs a PWMD signal. Understandably, this totem-pole off-grid inverter can complete the DC-to-AC conversion process. However, it currently generally uses continuous current mode, which suffers from high EMC interference, high losses on the switching transistors, and sometimes high-frequency switching transistors, resulting in higher costs.

[0121] Figure 2 This is a logic circuit diagram illustrating how a totem-pole off-grid inverter circuit operates in critical current mode using peak current, as described in an embodiment of this application. Figure 2As shown, the logic circuit mainly includes two comparators and one RS flip-flop. Specifically, the acquired output current is input into this logic circuit module for comparison. By comparing it with the peak current Ipeak of the first comparator and the zero value of the second comparator, two signals can be output, and the subsequent signal path is determined according to the direction of the peak current. When the direction of the peak current Ipeak is positive, the signal generated by the comparator will be transmitted on the positive path; when the direction of the peak current Ipeak is negative, the signal generated by the comparator will be transmitted on the negative path. Specifically, when the direction of the peak current Ipeak is positive, the controlled object is the first switching transistor, and the corresponding control output pulse signal is PWMA; when the direction of the peak current Ipeak is negative, the controlled object is the second switching transistor, and the corresponding control output pulse signal is PWMB. Inverting gates are provided on the negative path after the first comparator and the positive path after the second comparator to invert the signals, such as setting signal 1 to 0 or signal 0 to 1. A counter can be added to the path after the comparator to count the number of times the signal output from the second comparator is received. When the peak current direction Ipeak is negative, the signal output from the second comparator is the signal directly output by the second comparator. When the peak current direction Ipeak is positive, the signal output from the second comparator is the signal obtained by performing a NOT operation on the first signal output by the second comparator using an NOT gate. The signal is only allowed to be transmitted to the RS flip-flop when the counter reaches the count threshold. Specifically, the judgment logic of whether the counter has reached the count threshold can be implemented by setting an AND gate. The signal output from the second comparator is only sent to the RS flip-flop when the logical judgment condition of the AND gate is met, i.e., the signal output from the second comparator reaches the count threshold. In this application, the switching frequency of the switching transistor can be adjusted by the counter to avoid the switching transistor operating at a high switching frequency. After receiving the two input signals, the RS flip-flop will trigger the target output signal according to the signal result, so as to control the switching transistor according to the target output signal, so that the totem pole off-grid inverter circuit can automatically and stably operate in the critical current mode.

[0122] Specifically, by combining the peak current Ipeak with the output current IL and zero value under different conditions, the process of this logic circuit implementing critical current mode control can be clearly seen:

[0123] First, the truth operation corresponding to the RS flip-flop is:

[0124] When S=0 and R=0, the Q state remains unchanged;

[0125] When S=1 and R=0, the Q state is set to 1;

[0126] When S=0 and R=1, the Q state is set to 0;

[0127] When S=1 and R=1, the Q state is uncertain.

[0128] When Ipeak is the positive electrode, there are three cases:

[0129] IL>Ipeak, R=1, IL>0, S=0;

[0130] This situation indicates that IL exceeds Ipeak, meaning that the first switch has been on for too long and is supplying too much current. The first switch should be turned off when Q is 0, so that IL can be reduced from the peak current to 0.

[0131] IL<Ipeak,R=0,IL> 0, S = 0;

[0132] This situation indicates that the first switch is turned on and the current has not yet reached its peak value. The first switch can continue to be turned on so that IL approaches Ipeak.

[0133] IL <Ipeak,R=0,IL=0,S=1;

[0134] This situation indicates that after the first switch is turned off, the current drops to 0, which is the critical point. The control object can be switched from the first switch to the second switch, and the second switch can be turned on so that the current can reach Ipeak in the negative direction.

[0135] When Ipeak is the negative electrode, there are three cases:

[0136] IL>Ipeak, R=0, IL<0, S=0;

[0137] This situation indicates that the second switch is turned on and the current has not yet reached its peak value. The second switch can be kept on to allow IL to approach Ipeak.

[0138] IL <Ipeak,R=1,IL<0,S=0;

[0139] This situation indicates that the absolute value of IL exceeds the absolute value of Ipeak, meaning that the second switch has been on for too long and too much current is being supplied. The second switch should be turned off to allow IL to return from the peak current to 0.

[0140] IL>Ipeak, R=0, IL=0, S=1;

[0141] This situation indicates that the current returns to 0 after the second switch is turned off. This is the critical point. The control object can be switched from the second switch to the first switch, and the first switch can be turned on so that the current can reach Ipeak in the positive direction.

[0142] Through the above analysis of the logic execution of the logic circuit, it can be seen that the control result of the logic execution precisely realizes the circuit operating in the critical current mode. This critical current mode is achieved through automatic circuit adjustment, requiring no additional intervention from the user, and ensuring stable closed-loop execution throughout. In this embodiment, the fully automatic and stable execution of the critical current mode is achieved through peak current. Furthermore, by changing the peak current according to the critical current mode, the switching frequency of the switching transistor can be correspondingly altered, which helps reduce EMC interference.

[0143] Figure 3 This is a voltage loop control diagram of a totem pole off-grid inverter circuit according to an embodiment of this application. For example... Figure 3 As shown, this includes the output voltage Uo, the reference output voltage Uoref, and the voltage difference Uerr. By calculating the difference between the reference output voltage Uoref and the output voltage Uo, the voltage difference Uerr can be obtained. Inputting the voltage difference Uerr into the loop controller enables closed-loop adjustment of the voltage loop, making the output voltage Uo close to the reference output voltage Uoref. Therefore, the peak current Ipeak can be obtained based on the output voltage Uo. Figure 3 The diagram also illustrates the control of the current direction and the current directions of the third and fourth switches. When the peak current Ipeak is greater than 0, the peak current Ipeak direction is positive; when the peak current Ipeak is less than 0, the peak current Ipeak direction is negative. When the output voltage Uo is greater than zero, the fourth switch is turned on; when the output voltage Uo is less than zero, the third switch is turned on. This allows only one switch to be turned on per switching cycle in a critical current mode, reducing the shoot-through risk of the two switches in the bridge arm.

[0144] In this embodiment, peak current is used to control the totem-pole off-grid inverter circuit in a critical current mode. Specifically, the switching transistor to be controlled is first determined by the direction of the peak current. Then, based on the output current, the first comparison branch output signal and the second comparison branch output signal are obtained by comparing the peak current with a zero value. A target output signal is then triggered. Based on the target output signal and the direction of the peak current, the corresponding switching transistor is turned on, turned off, kept on, or kept off, thereby controlling the totem-pole off-grid inverter circuit in a critical current mode. This application enables the totem-pole off-grid inverter circuit to automatically adjust and control its operation in a critical current mode, effectively reducing EMC interference. Furthermore, since this application uses a zero-voltage turn-on switching transistor, the cost of the switching transistor can be reduced; and since this application uses peak current control, the current control capability is greatly enhanced, avoiding the problem of excessive stress on the switching transistor due to excessive current.

[0145] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0146] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is used as an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above.

[0147] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A critical current-mode control method for a totem-pole off-grid inverter circuit, characterized in that, include: Determine the peak current, wherein the peak current includes the positive direction or the negative direction. When the peak current is in the positive direction, the first switch is the controlled object. When the peak current is in the negative direction, the second switch is the controlled object. The first switch and the second switch form a half-bridge structure. The output current is acquired, and the output current is compared with the peak current to obtain a first comparison branch output signal. The output current is also compared with zero to obtain a second comparison branch output signal. The target output signal is triggered based on the first comparison branch output signal and the second comparison branch output signal; The control object is turned on or off according to the direction of the peak current and the target output signal, or the current control state of the control object is maintained, so that the totem pole off-grid inverter circuit operates in the critical current mode. In the same direction of the peak current, when the absolute value of the output current is greater than the absolute value of the peak current, the control object is turned off; when the absolute value of the output current is not greater than the absolute value of the peak current and is greater than the zero value, the control object maintains the current control state; when the output current is equal to the zero value, the direction of the peak current changes and the control object is turned on.

2. The method according to claim 1, characterized in that, The determination of the peak current includes: Obtain the output voltage setting command, and determine the reference output voltage according to the output voltage setting command; The output voltage is acquired and input into a voltage loop, wherein the voltage loop includes a loop controller; The output voltage is compared with the reference output voltage to obtain the voltage difference; The voltage difference is input into the loop controller to obtain the loop controller output; The peak current is determined based on the output of the loop controller.

3. The method according to claim 1, characterized in that, The step of comparing the output current with the peak current to obtain a first comparison branch output signal, and comparing the output current with zero to obtain a second comparison branch output signal, includes: The output current is input to a first comparator and a second comparator for comparison to obtain a first comparison branch output signal and a second comparison branch output signal, wherein the value used by the first comparator for comparison is the peak current, and the value used by the second comparator for comparison is the zero value; When the output current is greater than the peak current, the first comparison branch output signal is a high-level signal; when the output current is not greater than the peak current, the first comparison branch output signal is a low-level signal. When the output current is greater than the zero value, the second comparison branch output signal is a high-level signal; when the output current is not greater than the zero value, the second comparison branch output signal is a low-level signal.

4. The method according to claim 3, characterized in that, The first comparator has an NOT gate on the path of the peak current in the negative direction, the second comparator has an NOT gate on the path of the peak current in the positive direction, and the target output signal is triggered by an RS flip-flop.

5. The method according to claim 4, characterized in that, The step of triggering the target output signal based on the first comparison branch output signal and the second comparison branch output signal includes: Based on the direction of the peak current, the first comparison branch output signal, and the second comparison branch output signal, a first condition signal and a second condition signal are obtained. The first condition signal and the second condition signal are input into the RS flip-flop to trigger the target output signal.

6. The method according to claim 5, characterized in that, Before inputting the first condition signal and the second condition signal into the RS flip-flop to trigger the target output signal, the method further includes: The number of times the second condition signal is output is counted. When the number of outputs reaches a threshold, the second condition signal triggers an output condition, and the count value is cleared to zero.

7. The method according to any one of claims 1-6, characterized in that, The method further includes: Determine the output voltage; The fourth switch is turned on when the output voltage is greater than zero. When the output voltage is less than zero, the third switch is turned on. The third and fourth switches form a half-bridge structure, and the first, second, third, and fourth switches form a full-bridge structure. The first and fourth switches are diagonally opposite each other.

8. A totem pole off-grid inverter circuit, characterized in that, include: The system comprises a voltage source, a full-bridge structure, an output inductor, and a load resistor. The full-bridge structure includes a first switch, a second switch, a third switch, and a fourth switch, wherein the first switch and the fourth switch are diagonally opposite each other. A peak current determination module is used to determine a peak current, wherein the peak current includes a positive direction or a negative direction. When the peak current is in the positive direction, the first switch is the controlled object, and when the peak current is in the negative direction, the second switch is the controlled object. The first switch and the second switch are a half-bridge structure. The target output signal triggering module is used to acquire the output current, compare the output current with the peak current to obtain a first comparison branch output signal, and compare the output current with zero value to obtain a second comparison branch output signal, and trigger the target output signal according to the first comparison branch output signal and the second comparison branch output signal; A pulse output module is used to turn the controlled object on or off according to the direction of the peak current and the target output signal, or to maintain the current control state of the controlled object, so that the totem pole off-grid inverter circuit operates in critical current mode. Specifically, in the same direction of the peak current, when the absolute value of the output current is greater than the absolute value of the peak current, the controlled object is turned off; when the absolute value of the output current is not greater than the absolute value of the peak current but is greater than zero, the controlled object maintains its current control state; when the output current equals zero, the direction of the peak current changes, and the controlled object is turned on.

9. The circuit according to claim 8, characterized in that, The target output signal triggering module is also used for: Obtain the output voltage; When the output voltage is greater than zero, the fourth switch is turned on; When the output voltage is less than zero, the third switch is turned on, wherein the third switch and the fourth switch constitute the half-bridge structure.

10. The circuit according to claim 8, characterized in that, The target output signal triggering module includes a first comparator and a second comparator; The first comparator has an NOT gate on the path of the peak current in the negative direction, and the second comparator has an NOT gate on the path of the peak current in the positive direction. A counter is used to count the number of times the second condition signal is output. When the number of outputs reaches a threshold, the second condition signal triggers an output condition, and the count value of the counter is cleared to zero. The second condition signal is obtained based on the direction of the peak current and the second comparison branch output signal. An RS flip-flop is configured to receive the second condition signal and the first condition signal, and output a target output signal, wherein the first condition signal is obtained based on the direction of the peak current and the first comparison branch output signal.

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