Voltage zero crossing point detection device, voltage zero crossing point detection method and control system

Abstract

The invention relates to a voltage zero crossing point detection device, a voltage zero crossing point detection method and a control system. Wherein a complete period value of an alternating current signal before the captured Nth zero crossing point is obtained, and zero crossing point prediction is performed on the (N + 1) th zero crossing point, and the zero crossing point prediction comprises the following steps: starting timing when the Nth zero crossing point is captured, voltage sampling is carried out at the first duration and the second duration from the Nth zero crossing point to obtain a first voltage value and a second voltage value respectively, and the predicted zero crossing time of the (N + 1) th zero crossing point is obtained according to the complete period value, the first voltage value and the second voltage value, the predicted zero-crossing time is obtained before the actual zero-crossing time of the (N + 1)-th zero-crossing point arrives, so that the preparation for the operation to be adopted at the (N + 1)-th zero-crossing point in advance is facilitated, the accuracy of the zero-crossing point correlation operation is improved, and the influence caused by control lag can be reduced.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and in particular, to a voltage zero-crossing detection device, a voltage zero-crossing detection method, and a control system. Background Art

[0002] In the design and application of electronic circuits, when the input voltage is an AC signal, the zero position passed through when its waveform transitions from the positive half-cycle to the negative half-cycle and from the negative half-cycle to the positive half-cycle is the zero-crossing point. The system often needs to detect the moment when this zero-crossing point occurs, that is, perform zero-crossing detection, and information such as the phase, frequency, or jitter of the AC signal can be obtained. According to the zero-crossing detection result, a corresponding signal output is generated.

[0003] In traditional voltage zero-crossing detection methods, the input AC signal is conditioned by a conditioning circuit. Specifically, the AC signal is scaled proportionally and a bias voltage is added to raise the AC signal so that the potentials of the points on the positive and negative half-cycles of the waveform are both greater than 0. Among them, the potential of the points on the positive half-cycle is greater than the bias voltage, and the potential of the points on the negative half-cycle is less than the bias voltage. A comparator is used to compare the conditioned signal with the bias voltage, and based on the output of the comparator, the zero-crossing point where the input voltage transitions from the positive half-cycle to the negative half-cycle and the zero-crossing point where it transitions from the negative half-cycle to the positive half-cycle can be detected.

[0004] However, in actual circuits, when using the above traditional voltage zero-crossing detection method, the zero-crossing point can only be detected after it has been formed. After detecting the already-occurred zero-crossing point, the circuit and the controller are triggered to perform subsequent operations. Due to certain delays in the circuit and the controller code, there is a problem of control lag. Summary of the Invention

[0005] In order to avoid the control lag problem existing in performing zero-crossing related operations after detecting the already-occurred zero-crossing point and improve the accuracy of zero-crossing related operations, the present invention provides a voltage zero-crossing detection device and a voltage zero-crossing detection method. The present invention further provides a control system.

[0006] On the one hand, the present invention provides a voltage zero-crossing detection device, and the voltage zero-crossing detection device includes:

[0007] A timer;

[0008] An ADC module for sampling the voltage of the AC signal after it is raised above the zero level;

[0009] A processor for obtaining, via the timer, the complete cycle value of the AC signal before the Nth captured zero-crossing point, and performing zero-crossing prediction on the (N + 1)th zero-crossing point. The zero-crossing prediction includes:

[0010] When capturing the Nth zero crossing, trigger the timer to start timing;

[0011] Perform voltage sampling at a first time duration from the Nth zero crossing to obtain a first voltage value, and perform voltage sampling at a second time duration from the Nth zero crossing to obtain a second voltage value. The first time duration is less than 1 / 4 of the full cycle value, the second time duration is greater than 1 / 4 of the full cycle value, and the difference between 1 / 4 of the full cycle value and the first time duration is equal to the difference between the second time duration and 1 / 4 of the full cycle value; and

[0012] Obtain the predicted zero crossing time of the (N + 1)th zero crossing. The time duration from the Nth zero crossing to the predicted zero crossing time is (T / 2+(Ts1 - Ts2) / K1), where T is the full cycle value, Ts1 is the first voltage value, Ts2 is the second voltage value, K1 is the first coefficient, and N is a positive integer.

[0013] Optionally, the processor determines the full cycle value before the Nth zero crossing according to the captured Nth zero crossing; the processor is further configured to count the continuous (A + 1) cycle values of the AC signal. When the change amount of the (A + 1)th cycle value compared to the average value of the previous A cycle values is less than the first fluctuation threshold, start the zero crossing prediction process, and use the (A + 1)th cycle value as the full cycle value to at least predict the predicted zero crossing time of the first zero crossing in the zero crossing prediction process. When the change amount of the (A + 1)th cycle value compared to the average value of the previous A cycle values is greater than or equal to the first fluctuation threshold, do not start the zero crossing prediction process. A is a positive integer greater than 1.

[0014] Optionally, after predicting the zero crossing time of the (N + 1)th zero crossing, the zero crossing prediction further includes:

[0015] Capture the actual zero crossing time of the (N + 1)th zero crossing; and

[0016] Judge whether the time difference between the actual zero crossing time and the predicted zero crossing time of the (N + 1)th zero crossing exceeds the second fluctuation threshold. If it does not exceed the second fluctuation threshold, continue to predict the zero crossing time of the (N + 2)th zero crossing. If it exceeds the second fluctuation threshold, exit the zero crossing prediction process.

[0017] Optionally, predicting the zero crossing time of the (N + 2)th zero crossing includes:

[0018] When capturing the actual zero-crossing moment of the (N + 1)-th zero-crossing point, trigger the timer to start timing, use the (N + 1)-th zero-crossing point as the updated N-th zero-crossing point, collect the corresponding first voltage value and second voltage value, and predict the zero-crossing moment of the next zero-crossing point of the updated N-th zero-crossing point.

[0019] Optionally, when capturing the actual zero-crossing moment of the (N + 1)-th zero-crossing point, update the full cycle value to the duration of the previous full cycle before the actual zero-crossing moment of the (N + 1)-th zero-crossing point.

[0020] Optionally, predicting the zero-crossing moment of the (N + 2)-th zero-crossing point includes:

[0021] Perform voltage sampling at a third duration from the N-th zero-crossing point to obtain a third voltage value, and perform voltage sampling at a fourth duration from the N-th zero-crossing point to obtain a fourth voltage value. The third duration is greater than 1 / 2 of the full cycle value and less than 3 / 4 of the full cycle value, the fourth duration is greater than 3 / 4 of the full cycle value and less than the full cycle value, and the difference between 3 / 4 of the full cycle value and the third duration is equal to the difference between the fourth duration and 3 / 4 of the full cycle value; and

[0022] Predict that the duration of the zero-crossing moment of the (N + 2)-th zero-crossing point from the actual zero-crossing moment of the (N + 1)-th zero-crossing point is (T / 2 + (Ts3 - Ts4) / K2), where T is the full cycle value, Ts3 is the third voltage value, Ts4 is the fourth voltage value, and K2 is the second coefficient.

[0023] Optionally, when the change amount of the (A + 1)-th cycle value compared to the average value of the previous A cycle values is greater than or equal to the first fluctuation threshold, and after exiting the zero-crossing prediction process, the processor is further configured to output a zero-crossing signal according to the captured actual zero-crossing moment.

[0024] Optionally, the first duration is 1 / 8 of the full cycle value, and the second duration is 3 / 8 of the full cycle value; or, the first duration is 3 / 16 of the full cycle value, and the second duration is 5 / 16 of the full cycle value.

[0025] Optionally, the voltage zero-crossing detection device further includes:

[0026] A signal conditioning circuit for accessing the AC signal, amplifying or reducing the AC signal and superimposing a bias voltage to convert the AC signal into a conditioned signal above the zero level.

[0027] A comparator for comparing the conditioned signal with the bias voltage and forming a corresponding output signal;

[0028] Wherein, the zero-crossing of the AC signal is captured by detecting the rising edge or falling edge of the output signal of the comparator.

[0029] On the other hand, the present invention provides a method for detecting the zero-crossing of a voltage, and the method for detecting the zero-crossing of a voltage includes:

[0030] Obtaining the complete cycle value of the AC signal before the Nth captured zero-crossing, and predicting the zero-crossing of the (N + 1)th zero-crossing;

[0031] The zero-crossing prediction includes: starting timing when the Nth zero-crossing is captured;

[0032] Performing voltage sampling at a first time duration from the Nth zero-crossing to obtain a first voltage value, and performing voltage sampling at a second time duration from the Nth zero-crossing to obtain a second voltage value. The first time duration is less than 1 / 4 of the complete cycle value, the second time duration is greater than 1 / 4 of the complete cycle value, and the difference between 1 / 4 of the complete cycle value and the first time duration is equal to the difference between the second time duration and 1 / 4 of the complete cycle value; and

[0033] Obtaining the predicted zero-crossing moment of the (N + 1)th zero-crossing, and the time duration from the Nth zero-crossing to the predicted zero-crossing moment of the (N + 1)th zero-crossing is (T / 2+(Ts1 - Ts2) / K1), where T is the complete cycle value, Ts1 is the first voltage value, Ts2 is the second voltage value, K1 is a first coefficient, and N is a positive integer.

[0034] On the one hand, the present invention provides a control system, and the control system includes:

[0035] The above voltage zero-crossing detection device; and

[0036] A PFC control module for controlling a PFC circuit to operate. Wherein, the PFC control module obtains the predicted zero-crossing moment of the (N + 1)th zero-crossing obtained by the voltage zero-crossing detection device, and starts the operation associated with the (N + 1)th zero-crossing in advance before the predicted zero-crossing moment of the (N + 1)th zero-crossing, and completes the operation associated with the (N + 1)th zero-crossing at the actual zero-crossing moment of the (N + 1)th zero-crossing.

[0037] In the voltage zero-crossing detection device and the voltage zero-crossing detection method provided by the present invention, the complete cycle value of the AC signal before the Nth captured zero-crossing is obtained, and the (N + 1)th zero-crossing is predicted. When performing the zero-crossing prediction, timing starts when the Nth zero-crossing of the AC signal is captured, and voltage sampling is respectively performed at a first time duration and a second time duration from the Nth zero-crossing to obtain a first voltage value and a second voltage value. According to the complete cycle value and the first voltage value and the second voltage value, the predicted zero-crossing moment of the (N + 1)th zero-crossing is obtained. This predicted zero-crossing moment is obtained before the actual zero-crossing moment of the (N + 1)th zero-crossing arrives, which is convenient for deploying the operations associated with the (N + 1)th zero-crossing in advance, so that the operations associated with the (N + 1)th zero-crossing and the actual zero-crossing action can be more accurately synchronized and completed, improving the accuracy of the operations associated with the zero-crossing, and reducing the influence caused by control lag.

[0038] The control system provided by the present invention includes the above voltage zero-crossing detection device and a PFC control module. The PFC control module obtains the predicted zero-crossing moment of the (N + 1)th zero-crossing obtained by the voltage zero-crossing detection device, and starts to execute the operations associated with the (N + 1)th zero-crossing in advance before this predicted zero-crossing moment, which is convenient for accurately completing the operations associated with the (N + 1)th zero-crossing at the actual zero-crossing moment of the (N + 1)th zero-crossing, and helps to improve the effect of power factor correction. Description of the Drawings

[0039] Figure 1 It is a schematic structural diagram of a voltage zero-crossing detection device according to an embodiment of the present invention.

[0040] Figure 2A and Figure 2B They are respectively waveform diagrams of an AC signal and a conditioning signal in an embodiment of the present invention.

[0041] Figure 3A It is a schematic diagram of a comparator in an embodiment of the present invention.

[0042] Figure 3B It is an output waveform diagram of the comparator in an embodiment of the present invention.

[0043] Figure 4 It is a schematic diagram of the positions of zero-crossings and voltage sampling points in an embodiment of the present invention.

[0044] Figure 5 It is a schematic flow diagram of a voltage zero-crossing detection method in an embodiment of the present invention.

[0045] Figure 6 It is a schematic diagram of a control system in an embodiment of the present invention. Detailed Embodiments

[0046] The following further elaborates on the voltage zero-crossing detection device, voltage zero-crossing detection method, and control system of the present invention in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise scales, only for conveniently and clearly assisting in explaining the purpose of the embodiments of the present invention.

[0047] Voltage zero-crossing detection technology has currently been applied in many fields. For example, in some intelligent switches and intelligent on-off devices, zero-voltage on-off is achieved through zero-crossing detection to suppress inrush current at startup, suppress arcs and instantaneous high temperatures, and achieve the purpose of protecting devices; in the field of intelligent lighting, dimming devices apply zero-crossing detection technology to control the conduction angle of alternating current starting from zero to achieve brightness adjustment; in the field of industrial control, zero-crossing detection is used to judge the output of synchronous signals to achieve motor speed adjustment; also, for example, in the power supply field, the totem pole PFC control algorithm that can greatly improve efficiency is used to control the power factor correction (PFC) circuit. The totem pole PFC control algorithm adopts different control strategies for the positive and negative half-cycles of the input signal. Therefore, it is necessary to detect the precise zero-crossing point of the input signal to adjust the control strategy.

[0048] The voltage zero-crossing detection device and voltage zero-crossing detection method involved in the embodiments of the present invention can detect the zero-crossing point of an AC signal in the above fields or other suitable fields. Among them, in order to avoid the problems of response lag and control lag that exist when subsequent operations are carried out after detecting an already-occurred zero-crossing point, and improve the accuracy of zero-crossing related operations, zero-crossing prediction is performed to predict the zero-crossing moment of the zero-crossing point. The prediction result is obtained before the actual zero-crossing moment of this zero-crossing point arrives, which is convenient for deploying the operations related to this zero-crossing point in advance, can improve the accuracy of zero-crossing related operations, and reduce the influence caused by response lag and control lag.

[0049] Refer to Figure 1, in the embodiment of the present invention, the zero-crossing voltage detection device includes, for example, a digital controller (more specifically, an MCU for example), and the digital controller further includes a timer, an ADC module, and a processor. The ADC module is used to sample the voltage after the AC signal is raised above the zero level. The processor is used to obtain the complete cycle value of the AC signal before the Nth zero-crossing captured via the timer, and perform zero-crossing prediction on the (N + 1)th zero-crossing. The counting start value of "the Nth" in the Nth zero-crossing can be set. Specifically, in one embodiment, the processor determines the complete cycle value before the Nth zero-crossing according to the captured Nth zero-crossing, that is to say, the complete cycle value can be the duration of one complete cycle with the captured Nth zero-crossing as the end time.

[0050] In an alternative embodiment, the processor first enters a zero-crossing prediction process and then performs zero-crossing prediction. For example, when the signal conditioning circuit and the MCU are just powered on or the power grid itself fluctuates greatly, since the cycle fluctuation of the AC signal is usually large, at this time, the zero-crossing signal can be output according to the actual zero-crossing detected by the timer, and it is judged whether it is possible to enter a zero-crossing prediction process. During the zero-crossing prediction process, the zero-crossing times of one or two or more consecutive zero-crossings can be predicted. The (N + 1)th zero-crossing is the zero-crossing in the zero-crossing prediction process, and can be, for example, the first zero-crossing, the second zero-crossing, etc. in the zero-crossing prediction process.

[0051] Specifically, the processor is further used to count the continuous (A + 1) cycle values of the AC signal, calculate the average value Tave of the first A cycle values. After obtaining the (A + 1)th cycle value T(A + 1), compare the change amount of the (A + 1)th cycle value T(A + 1) compared with the average value Tave. When the change amount of the (A + 1)th cycle value T(A + 1) compared with the average value Tave of the previous A cycle values is less than the first fluctuation threshold ERR1, that is, |T(A + 1) - Tave| < ERR1, start the zero-crossing prediction process, and use the (A + 1)th cycle value as the complete cycle value to at least predict the predicted zero-crossing time of the first zero-crossing in the zero-crossing prediction process; when the change amount of the (A + 1)th cycle value compared with the average value of the previous A cycle values is greater than or equal to the first fluctuation threshold, that is, |T(A + 1) - Tave| ≧ ERR1, it indicates that the current cycle fluctuation is large and not suitable for zero-crossing prediction, so the zero-crossing prediction process is not started. A is a positive integer greater than 1. The first fluctuation threshold ERR1 can be set according to specific circumstances.

[0052] The complete cycle value obtained according to the (A + 1)-th cycle value can also be used to predict the zero-crossing moments of other zero-crossing points in the zero-crossing prediction process. However, the present invention is not limited thereto. Optionally, when capturing the actual zero-crossing moment of the (N + 1)-th zero-crossing point, the complete cycle value is updated to the duration of the previous complete cycle before the actual zero-crossing moment of the (N + 1)-th zero-crossing point, so as to improve the prediction accuracy.

[0053] When the zero-crossing moment of a zero-crossing point is predicted, the processor can output a zero-crossing prediction signal. Optionally, the processor is further configured to output a zero-crossing signal according to the captured actual zero-crossing point when the change amount of the (A + 1)-th cycle compared with the average value of the previous A cycle values is greater than or equal to the first fluctuation threshold, and after exiting (i.e., ending) the zero-crossing prediction process.

[0054] Optionally, as Figure 1 shown, the voltage zero-crossing detection device may further include a signal conditioning circuit and a comparator. The signal conditioning circuit is configured to access the AC signal to be detected for zero-crossing points, amplify or reduce the AC signal and superimpose a bias voltage to convert the AC signal into a conditioned signal above the zero level. Referring to Figure 2A , the voltage Vac of the AC signal to be detected for zero-crossing points changes sinusoidally with time t, and each complete cycle thereof includes two zero-crossing points, namely the zero-crossing point from the negative half-cycle to the positive half-cycle (shown as "zero+" in Figure 2) and the zero-crossing point from the positive half-cycle to the negative half-cycle (shown as "zero-" in Figure 2). As an example, in one embodiment, the signal conditioning circuit accesses the AC signal, reduces the amplitude of the AC signal, and superimposes a bias voltage of 1.65V on the AC signal with reduced amplitude, then a conditioned signal above the zero level as shown in Figure 2B is obtained. The voltage U of the conditioned signal changes sinusoidally with time t, and the voltage values of all points are greater than 0. After conditioning, the occurrence positions of the zero-crossing points of the AC signal remain unchanged. The signal conditioning circuit can adopt various circuit designs capable of realizing the above functions.

[0055] Referring to Figure 3A and Figure 3B , the comparator is configured to compare the conditioned signal with the bias voltage and form a corresponding output signal. It can be understood that the positive and negative half-cycles of the conditioned signal are converted at the level position of the bias voltage, so that the output signal of the comparator undergoes a level conversion when the conditioned signal crosses zero (i.e., when the AC signal before conditioning crosses zero). By detecting the rising edge and falling edge of the output signal of the comparator, the zero-crossing points of the AC signal can be captured. Figure 3BThe position pointed by the arrow in the figure is the zero crossing point. In this embodiment, for example, the timer is used to detect the rising edge or falling edge of the output signal of the comparator to capture the zero crossing point of the AC signal. By capturing the zero crossing point, the actual zero crossing moment of the corresponding zero crossing point is detected. By counting the count values of the timer corresponding to two consecutive rising edges or two consecutive falling edges, the period value of the AC signal can be obtained. Since the corresponding zero crossing action has occurred when the rising edge or falling edge of the output signal of the comparator is detected, using the timer to detect the zero crossing point is a passive detection method. In this embodiment, the voltage zero crossing detection device can use the timer to detect the zero crossing point, that is, it includes a passive detection method, and the processor can perform zero crossing prediction, predicting the zero crossing moment of the zero crossing point before the actual zero crossing moment of the zero crossing point arrives. Therefore, the voltage zero crossing detection device also includes an active detection method.

[0056] The voltage zero crossing detection device can be coupled to another control module, and this another control module performs corresponding operations according to the actual zero crossing moment or predicted zero crossing moment output by the processor. The present invention is not limited to this. In other embodiments, this another control module can also be integrated in the voltage zero crossing detection device. For example, the foregoing zero crossing detection is performed by the same processor and corresponding operations are performed according to the zero crossing detection result. Specifically, before entering the zero crossing prediction process and after exiting the zero crossing prediction process, the processor can output a zero crossing signal (such as the actual zero crossing moment) to this another control module according to the zero crossing point of the AC signal detected by the timer. At this time, the control is relatively lagging. During the zero crossing prediction process, the processor can output a zero crossing prediction signal (such as the predicted zero crossing moment) to this another control module according to the prediction result, so that this another control module can start performing operations related to the zero crossing point in advance, which can reduce the risk of control lag.

[0057] Performing zero crossing prediction on the (N + 1)th zero crossing point may specifically include the following process:

[0058] First, when capturing the Nth zero crossing point, trigger the timer to start timing;

[0059] Next, voltage sampling is performed at a first time length from the Nth zero crossing point to obtain a first voltage value, and voltage sampling is performed at a second time length from the Nth zero crossing point to obtain a second voltage value. The first time length is less than 1 / 4 of the complete cycle value, the second time length is greater than 1 / 4 of the complete cycle value, and the difference between 1 / 4 of the complete cycle value and the first time length is equal to the difference between the second time length and 1 / 4 of the complete cycle value. The first time length and the second time length can be calculated according to the program inside the processor, and the ADC module can be used for voltage sampling;

[0060] After that, the predicted zero-crossing moment of the (N + 1)-th zero-crossing point is obtained. The time duration from the N-th zero-crossing point to the predicted zero-crossing moment is (T / 2 + (Ts1 - Ts2) / K1), where T is the value of the complete period, Ts1 is the first voltage value, Ts2 is the second voltage value, K1 is the first coefficient, and A and N are positive integers.

[0061] In the above process, the time duration from the N-th zero-crossing point refers to the time duration from the actual zero-crossing moment of the N-th zero-crossing point. The actual zero-crossing moment is the moment when the N-th zero-crossing point is captured. Since the timer starts timing when the N-th zero-crossing point is captured, the time duration from the N-th zero-crossing point is the time duration from the timing zero point formed by the timer due to capturing the N-th zero-crossing point.

[0062] Refer to Figure 4 , as an example, the first time duration is 1 / 8 of the complete period value (i.e., T / 8), the second time duration is 3 / 8 of the complete period value (3T / 8), and the first voltage value and the second voltage value are the voltage sampling values at T / 8 and 3T / 8 after the N-th zero-crossing point respectively. The present invention is not limited thereto, and the first time duration and the second time duration can also be set to other values. For example, in one embodiment, the first time duration is 3 / 16 of the complete period value, and the second time duration is 5 / 16 of the complete period value.

[0063] It can be understood that after a complete period ends, if the period value remains unchanged in the next complete period, then after the next complete period starts, the AC signal reaches the maximum voltage amplitude after 1 / 4 of the complete period value. The voltage values at the above first time duration and the above second time duration are two symmetric points on both sides of the maximum voltage amplitude on the positive or negative half cycle of the waveform, and the above first voltage value and the second voltage value are equal. However, in fact, the period value of the next complete period may remain unchanged or may change. Therefore, in the next complete period, the voltage values at the above first time duration and the above second time duration may be symmetric or asymmetric, and the first voltage value may be greater than, equal to, or less than the second voltage value. Conversely, according to the difference between the first voltage value and the second voltage value, it can be inferred that the next complete period is shorter (corresponding to an earlier zero-crossing point), unchanged, or longer (corresponding to a delayed zero-crossing point) compared to the previous period.

[0064] In this embodiment, the time length from the predicted zero-crossing moment of the (N+1)th zero-crossing point to the Nth zero-crossing point is (T / 2+(Ts1-Ts2) / K1), where T / 2 is half of the complete cycle value obtained before the Nth zero-crossing point, that is, the time length from the Nth zero-crossing point to the (N+1)th zero-crossing point when the actual cycle starting from the Nth zero-crossing point has not changed compared to the complete cycle value, (Ts1-Ts2) / K1 represents the compensation amount for the zero-crossing moment of the (N+1)th zero-crossing point when the period value of the actual period starting from the Nth zero-crossing point may be shortened or extended compared to the complete period value T, and when the period value of the actual period starting from the (N+1)th zero-crossing point is unchanged compared to the complete period value T, (Ts1-Ts2) / K1 is 0.

[0065] K1 can be obtained by fitting empirical data or by using trigonometric functions. Specifically, the phase difference between the first voltage value Ts1 and the second voltage value Ts1 can be calculated by combining the relationship between the phase and amplitude of the sine wave function. Since the sampling time of the first voltage value Ts1 and the second voltage value Ts1 is known, the value, actual period and zero crossing point of K1 can be derived. Figure 4 As shown, taking the case where the first time length is 1 / 8 of a complete cycle value (i.e., T / 8), the second time length is 3 / 8 of a complete cycle value (3T / 8), the first voltage value and the second voltage value are respectively the voltage sampling values at T / 8 and 3T / 8 after the Nth zero crossing point, as an example, the voltage waveform is converted from the negative half cycle to the positive half cycle at the Nth zero crossing point, and the mathematical expression of K1 is as follows:

[0066]

[0067] T in the above expression is the complete cycle value obtained before the Nth zero crossing point, and ts1 and ts2 are the normalized results of Ts1 and Ts2, because the ADC samples the sine wave after signal conditioning (the amplitude scaling and offset are modified). The specific normalization method is that ts is equal to Ts minus the bias voltage (such as 1.65V), and then divided by half of the peak-to-peak value Vpp of the conditioned signal (the Vpp value is known and determined by the parameters of the aforementioned signal conditioning circuit). Specifically, ts1 in the above formula = (Ts1-1.65) / (2*Vpp), ts2 = (Ts2-1.65) / (2*Vpp).

[0068] After predicting the predicted zero-crossing moment of the (N + 1)-th zero-crossing point, further, subsequent zero-crossing points can be continuously predicted. To avoid prediction distortion caused by excessive error between the predicted zero-crossing moment and the actual zero-crossing moment for each prediction, after predicting the zero-crossing moment of the (N + 1)-th zero-crossing point using the above process, the zero-crossing point prediction further includes: capturing the actual zero-crossing moment of the (N + 1)-th zero-crossing point, and determining whether the time difference between the actual zero-crossing moment of the (N + 1)-th zero-crossing point and the above predicted zero-crossing moment exceeds a second fluctuation threshold (denoted as ERR2). If it does not exceed the second fluctuation threshold, continue to predict the zero-crossing moment of the (N + 2)-th zero-crossing point. If it exceeds the second fluctuation threshold, it indicates that the voltage frequency fluctuation of the power grid at this time exceeds the expectation, and then exit the current zero-crossing prediction process. The second fluctuation threshold can be set according to specific circumstances.

[0069] Referring to Figure 4 , in one embodiment, after obtaining the predicted zero-crossing moment of the (N + 1)-th zero-crossing point and determining that the time difference between the actual zero-crossing moment of the (N + 1)-th zero-crossing point and the predicted zero-crossing moment does not exceed the second fluctuation threshold, further prepare to predict the zero-crossing moment of the (N + 2)-th zero-crossing point, which specifically includes:

[0070] First, perform voltage sampling at a third time length from the N-th zero-crossing point to obtain a third voltage value, and perform voltage sampling at a fourth time length from the N-th zero-crossing point to obtain a fourth voltage value. The third time length is greater than 1 / 2 of the complete cycle value and less than 3 / 4 of the complete cycle value, the fourth time length is greater than 3 / 4 of the complete cycle value and less than the complete cycle value, and the difference between 3 / 4 of the complete cycle value and the third time length is equal to the difference between the fourth time length and 3 / 4 of the complete cycle value;

[0071] After that, predict that the time length from the actual zero-crossing moment of the (N + 1)-th zero-crossing point to the zero-crossing moment of the (N + 2)-th zero-crossing point is (T / 2 + (Ts3 - Ts4) / K2), where T is the complete cycle value, Ts3 is the third voltage value, Ts4 is the fourth voltage value, and K2 is the second coefficient.

[0072] Referring to Figure 4 , as an example, the third time length is 5 / 8 of the complete cycle value (i.e., 5T / 8), the fourth time length is 7 / 8 of the complete cycle value (7T / 8), and the third voltage value and the fourth voltage value are the voltage sampling values at 5T / 8 and 7T / 8 after the N-th zero-crossing point respectively. The present invention is not limited thereto, and the third time length and the fourth time length can also be set to other values. For example, in one embodiment, the third time length is 11 / 16 of the complete cycle value, and the fourth time length is 13 / 16 of the complete cycle value.

[0073] In this embodiment, the duration from the zero-crossing moment of the (N + 2)-th zero-crossing point prediction to the actual zero-crossing moment of the (N + 1)-th zero-crossing point is (T / 2 + (Ts3 - Ts4) / K2), where T / 2 is half of the complete period value T, that is, the duration from the (N + 1)-th zero-crossing point to the (N + 2)-th zero-crossing point when the period value of the actual period starting from the N-th zero-crossing point remains unchanged. (Ts3 - Ts4) / K2 represents the compensation amount for the zero-crossing moment of the (N + 2)-th zero-crossing point when the period value of the actual period starting from the N-th zero-crossing point may be shortened or extended compared with the complete period value T. When the period value of the actual period starting from the N-th zero-crossing point is unchanged compared with the complete period value T, (Ts3 - Ts4) / K2 is 0. K2 can be obtained by fitting empirical data or calculated using trigonometric functions. Specifically, by using the difference between the third voltage value Ts3 and the fourth voltage value Ts4 and combining the relationship between the phase and amplitude of the sine wave function, the phase difference between the corresponding two sampling points can be calculated. Since the sampling time points of the third voltage value Ts3 and the fourth voltage value Ts4 are known, the value of K2, the actual period, and the zero-crossing point can be deduced. As Figure 4 shown, taking the case where the third duration is 5 / 8 of the complete period value (i.e., 5T / 8), the fourth duration is 7 / 8 of the complete period value (7T / 8), and the third voltage value and the fourth voltage value are the voltage sampling values at 5T / 8 and 7T / 8 after the N-th zero-crossing point as an example, the voltage waveform changes from the positive half-cycle to the negative half-cycle at the (N + 1)-th zero-crossing point, and the mathematical expression of K2 is as follows:

[0074]

[0075] The T appearing in the expression of this K2 is the complete period value obtained before the N-th zero-crossing point. ts3 and ts4 are the normalized results of Ts3 and Ts4 because the ADC samples the sine wave after signal conditioning (both the amplitude scaling and offset are modified). The specific normalization method is that ts is equal to Ts minus the offset voltage (such as 1.65V), and then divided by half of the peak-to-peak value Vpp of the conditioned signal (the value of Vpp is known and determined by the parameters of the aforementioned signal conditioning circuit). Specifically, ts3 = (Ts3 - 1.65) / (2*Vpp) and ts4 = (Ts4 - 1.65) / (2*Vpp) in the above formula.

[0076] Predicting the zero-crossing time of the (N + 2)-th zero-crossing is not limited to the above process. To further improve the prediction accuracy, after the (N + 1)-th zero-crossing is actually formed, the above process of predicting the (N + 1)-th zero-crossing can be looped to predict the zero-crossing time of the (N + 2)-th zero-crossing. Specifically, in one embodiment, after predicting the zero-crossing time of the (N + 1)-th zero-crossing, through judgment, it is determined that the time difference between the actual zero-crossing time and the predicted zero-crossing time of the (N + 1)-th zero-crossing does not exceed the second fluctuation threshold. Taking the (N + 1)-th zero-crossing as the updated N-th zero-crossing, loop the above process of predicting the (N + 1)-th zero-crossing. When capturing the (N + 1)-th zero-crossing, trigger the timer to start timing, and perform voltage sampling at a corresponding first duration from the updated N-th zero-crossing to obtain a corresponding first voltage value, and perform voltage sampling at a corresponding second duration from the updated N-th zero-crossing to obtain a corresponding second voltage value. Then predict the zero-crossing time of the next zero-crossing of the updated N-th zero-crossing, and this zero-crossing time is the zero-crossing time of the original (N + 2)-th zero-crossing. Predict the duration from it to the updated N-th zero-crossing as (T / 2 + (Ts1 - Ts2) / K1).

[0077] Through the above zero-crossing prediction process, after a zero-crossing, i.e., the N-th zero-crossing actually crosses zero, the zero-crossing time of the next zero-crossing, i.e., the (N + 1)-th zero-crossing, can be predicted. Moreover, after this next zero-crossing occurs, and within the allowable range of periodic fluctuations, the above zero-crossing prediction process can be looped to predict the zero-crossing time of the next-next zero-crossing. By predicting the zero-crossing time of the (N + 1)-th zero-crossing before its actual zero-crossing time arrives, it is convenient to prepare in advance for the operations to be taken at the (N + 1)-th zero-crossing, so that the operations to be taken at the (N + 1)-th zero-crossing can be more precisely synchronized with the zero-crossing action, improving the accuracy of zero-crossing related operations and reducing the influence caused by response and control lags.

[0078] An embodiment of the present invention further relates to a control system, which includes the voltage zero-crossing detection device described in the above embodiment and a PFC control module. The PFC control module is used to control the operation of a PFC circuit. Among them, the PFC control module obtains the predicted zero-crossing moment of the (N + 1)-th zero-crossing obtained by the voltage zero-crossing detection device, and starts the operation associated with the (N + 1)-th zero-crossing in advance before the predicted zero-crossing moment of the (N + 1)-th zero-crossing, and completes the operation associated with the (N + 1)-th zero-crossing at the actual zero-crossing moment of the (N + 1)-th zero-crossing. Specifically, during the zero-crossing prediction process, the voltage zero-crossing detection device can output a zero-crossing prediction signal to the PFC control module. The PFC control module performs related operations in advance according to the devices to be controlled and control methods in different half-cycles, such as sampling the output of the PFC circuit in advance, performing PID closed-loop calculation, and calculating the duty cycle of the PWM, so that when the zero-crossing action occurs, a corresponding PWM signal is output to the PFC circuit accurately and without delay, avoiding the problem of control lag, thereby helping to improve the effect of power factor correction.

[0079] In the control system, the voltage zero-crossing detection device and the PFC control module can be respectively arranged in different modules, or can be arranged in the same module. Refer to Figure 6 , in one embodiment, the PFC control module can be included in the voltage zero-crossing detection device and implemented by the above-mentioned processor. However, it is not limited to this. In another embodiment, the PFC control module is implemented by a processor outside the voltage zero-crossing detection device.

[0080] An embodiment of the present invention further relates to a voltage zero-crossing detection method, which can be implemented by using the above-mentioned voltage zero-crossing detection device. Refer to Figure 5 , the voltage zero-crossing detection method includes:

[0081] Obtain the complete cycle value of the AC signal before the captured N-th zero-crossing, and perform zero-crossing prediction on the (N + 1)-th zero-crossing. In a preferred embodiment, the voltage zero-crossing detection method can also perform zero-crossing detection by capturing the actual zero-crossing. In order to perform zero-crossing prediction, the continuous (A + 1) cycle values of the AC signal can be statistically counted first, and it is judged whether the change amount (|T(A + 1)-Tave|) of the (A + 1)-th cycle value compared with the average value of the previous A cycle values is less than the first fluctuation threshold ERR1 (that is, whether |T(A + 1)-Tave|<ERR1 holds). If so, enter a zero-crossing prediction process and perform zero-crossing prediction on the (N + 1)-th zero-crossing. If not, continue to statistically count the zero-crossing cycles;

[0082] Performing the zero-crossing prediction includes:

[0083] When capturing the Nth zero crossing of the AC signal, start timing;

[0084] Perform voltage sampling at a first duration from the Nth zero crossing to obtain a first voltage value, and perform voltage sampling at a second duration from the Nth zero crossing to obtain a second voltage value. The first duration is less than 1 / 4 of the full cycle value, the second duration is greater than 1 / 4 of the full cycle value, and the difference between 1 / 4 of the full cycle value and the first duration is equal to the difference between the second duration and 1 / 4 of the full cycle value; and

[0085] Obtain the predicted zero crossing time of the (N + 1)th zero crossing. The duration from the Nth zero crossing to the predicted zero crossing time is (T / 2+(Ts1 - Ts2) / K1), where T is the full cycle value, Ts1 is the first voltage value, Ts2 is the second voltage value, K1 is the first coefficient, and N is a positive integer.

[0086] The full cycle value is preferably the duration of the closest full cycle before the Nth zero crossing. As an example, the first duration is 1 / 8 of the full cycle value, and the second duration is 3 / 8 of the full cycle value. However, it is not limited to this. In one embodiment, the first duration is 3 / 16 of the full cycle value, and the second duration is 5 / 16 of the full cycle value.

[0087] After obtaining the predicted zero crossing time of the (N + 1)th zero crossing, the zero crossing times of subsequent zero crossings can be further predicted. To avoid prediction distortion caused by too large an error between the predicted zero crossing time and the actual zero crossing time each time, refer to Figure 5 , after obtaining the predicted zero crossing time of the (N + 1)th zero crossing using the above method, it may further include: capturing the actual zero crossing time of the (N + 1)th zero crossing; then, determining whether the time difference between the actual zero crossing time of the (N + 1)th zero crossing and the predicted zero crossing time exceeds a second fluctuation threshold. If it does not exceed the second fluctuation threshold, continue to predict the zero crossing time of the (N + 2)th zero crossing. If it exceeds the second fluctuation threshold, exit the zero crossing prediction process (i.e., stop zero crossing prediction).

[0088] In this embodiment, predicting the zero-crossing time of the (N + 2)-th zero-crossing point includes, for example: taking the (N + 1)-th zero-crossing point as the updated N-th zero-crossing point, and looping the process of predicting the zero-crossing time of the (N + 1)-th zero-crossing point based on the N-th zero-crossing point. For example, start timing when capturing the (N + 1)-th zero-crossing point, take the (N + 1)-th zero-crossing point as the updated N-th zero-crossing point, collect the corresponding first voltage value and second voltage value, and predict the zero-crossing time of the next zero-crossing point. In this embodiment, when capturing the actual zero-crossing time of the (N + 1)-th zero-crossing point, the complete cycle value T required for predicting subsequent zero-crossing points can also be updated to the duration of the previous complete cycle before the actual zero-crossing time of the (N + 1)-th zero-crossing point. In one embodiment, the complete cycle value can be the duration of one complete cycle with the actual zero-crossing time of the captured (N + 1)-th zero-crossing point as the end time, that is, the timing duration between the actual zero-crossing time of the (N + 1)-th zero-crossing point captured by the timer and the (N - 1)-th zero-crossing point is used as the complete cycle value.

[0089] In another embodiment, at the actual zero-crossing time of the (N + 1)-th zero-crossing point, instead of re-timing, the time when starting to time when capturing the N-th zero-crossing point is used. In this embodiment, predicting the zero-crossing time of the (N + 2)-th zero-crossing point includes, for example: performing voltage sampling at a third duration from the N-th zero-crossing point to obtain a third voltage value, and performing voltage sampling at a fourth duration from the N-th zero-crossing point to obtain a fourth voltage value. The third duration is greater than 1 / 2 of the complete cycle value and less than 3 / 4 of the complete cycle value, the fourth duration is greater than 3 / 4 of the complete cycle value and less than the complete cycle value, and the difference between 3 / 4 of the complete cycle value and the third duration is equal to the difference between the fourth duration and 3 / 4 of the complete cycle value; then, predict that the duration of the predicted zero-crossing time of the (N + 2)-th zero-crossing point from the actual zero-crossing time of the (N + 1)-th zero-crossing point is (T / 2 + (Ts3 - Ts4) / K2), where T is the complete cycle value, Ts3 is the third voltage value, Ts4 is the fourth voltage value, and K2 is the second coefficient. As an example, the third duration is 5 / 8 of the complete cycle value (i.e., 5T / 8), the fourth duration is 7 / 8 of the complete cycle value (7T / 8), and the third voltage value and the fourth voltage value are the voltage sampling values at 5T / 8 and 7T / 8 after the N-th zero-crossing point respectively. The present invention is not limited thereto, and the third duration and the fourth duration can also be set to other values. For example, in one embodiment, the third duration is 11 / 16 of the complete cycle value, and the fourth duration is 13 / 16 of the complete cycle value.

[0090] After predicting the zero-crossing time of the (N + 2)-th zero-crossing point, the zero-crossing times of subsequent zero-crossing points such as the (N + 3)-th zero-crossing point and the (N + 4)-th zero-crossing point can be further predicted as needed using the above method.

[0091] Using the voltage zero-crossing detection method described in the above embodiments, the zero-crossing time of the (N + 1)-th zero-crossing point is predicted before the actual zero-crossing time of the (N + 1)-th zero-crossing point arrives. The prediction result accurately reflects the zero-crossing time of the (N + 1)-th zero-crossing point, facilitating the preparation for the operations to be taken at the (N + 1)-th zero-crossing point in advance, so that the operations to be taken at the (N + 1)-th zero-crossing point and the zero-crossing action can be more precisely synchronized, improving the accuracy of zero-crossing related operations and reducing the impact caused by response and subsequent lag.

[0092] It should be noted that the embodiments in this specification are described in a progressive manner. Each part focuses on the differences from the previous part. For the same and similar parts between each part, reference can be made to each other.

[0093] The above description is only a description of the preferred embodiments of the present invention and does not limit the scope of the rights of the present invention in any way. Any person skilled in the art can make possible changes and modifications to the technical solution of the present invention using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention all fall within the protection scope of the technical solution of the present invention.

Claims

1. A zero-crossing voltage detection device, characterized in that, Comprising: A timer; An ADC module for sampling the voltage after the AC signal is raised above zero level; A processor for obtaining, via the timer, the complete cycle value of the AC signal before the Nth zero crossing being captured, and performing zero crossing prediction on the (N + 1)th zero crossing, the zero crossing prediction including: When capturing the Nth zero crossing, triggering the timer to start timing; Performing voltage sampling at a first duration from the Nth zero crossing to obtain a first voltage value, and performing voltage sampling at a second duration from the Nth zero crossing to obtain a second voltage value, the first duration being less than 1 / 4 of the complete cycle value, the second duration being greater than 1 / 4 of the complete cycle value, and the difference between 1 / 4 of the complete cycle value and the first duration being equal to the difference between the second duration and 1 / 4 of the complete cycle value; and Deriving the predicted zero crossing moment of the (N + 1)th zero crossing, the duration of the predicted zero crossing moment from the Nth zero crossing being (T / 2+(Ts1 - Ts2) / K1), T being the complete cycle value, Ts1 being the first voltage value, Ts2 being the second voltage value, K1 being the first coefficient, and N being a positive integer.

2. The voltage zero-crossing detection device according to claim 1, wherein The processor determines the complete cycle value before the Nth zero crossing according to the captured Nth zero crossing; the processor is further configured to count the continuous (A + 1) cycle values of the AC signal, and when the change amount of the (A + 1)th cycle value compared with the average value of the previous A cycle values is less than the first fluctuation threshold, start the zero crossing prediction process, and use the (A + 1)th cycle value as the complete cycle value to at least predict the predicted zero crossing moment of the first zero crossing in the zero crossing prediction process, and when the change amount of the (A + 1)th cycle value compared with the average value of the previous A cycle values is greater than or equal to the first fluctuation threshold, do not start the zero crossing prediction process, where A is a positive integer greater than 1.

3. The voltage zero-crossing detection device according to claim 1, characterized in that After predicting the zero crossing moment of the (N + 1)th zero crossing, the zero crossing prediction further includes: Capturing the actual zero crossing moment of the (N + 1)th zero crossing; and Judging whether the time difference between the actual zero crossing moment and the predicted zero crossing moment of the (N + 1)th zero crossing exceeds the second fluctuation threshold. If it does not exceed the second fluctuation threshold, continue to predict the zero crossing moment of the (N + 2)th zero crossing. If it exceeds the second fluctuation threshold, exit the zero crossing prediction process.

4. The voltage zero-crossing detection device according to claim 3, characterized in that, Predicting the zero crossing moment of the (N + 2)th zero crossing includes: When capturing the actual zero crossing moment of the (N + 1)th zero crossing, triggering the timer to start timing, using the (N + 1)th zero crossing as the updated Nth zero crossing, collecting the corresponding first voltage value and second voltage value, and predicting the zero crossing moment of the next zero crossing of the updated Nth zero crossing.

5. The voltage zero-crossing detection device according to claim 3, wherein, When capturing the actual zero crossing moment of the (N + 1)th zero crossing, updating the complete cycle value to the duration of the previous complete cycle before the actual zero crossing moment of the (N + 1)th zero crossing.

6. The voltage zero-crossing detection device according to claim 3, wherein, Predicting the zero-crossing time of the (N + 2)-th zero-crossing point includes: Performing voltage sampling at a third time duration from the N-th zero-crossing point to obtain a third voltage value, and performing voltage sampling at a fourth time duration from the N-th zero-crossing point to obtain a fourth voltage value. The third time duration is greater than 1 / 2 of the full cycle value and less than 3 / 4 of the full cycle value, the fourth time duration is greater than 3 / 4 of the full cycle value and less than the full cycle value, and the difference between 3 / 4 of the full cycle value and the third time duration is equal to the difference between the fourth time duration and 3 / 4 of the full cycle value; and Predicting that the time duration from the actual zero-crossing time of the (N + 1)-th zero-crossing point to the zero-crossing time of the (N + 2)-th zero-crossing point is (T / 2 + (Ts3 - Ts4) / K2), where T is the full cycle value, Ts3 is the third voltage value, Ts4 is the fourth voltage value, and K2 is the second coefficient.

7. The voltage zero-crossing detection device according to claim 3, wherein When the change amount of the (A + 1)-th cycle value compared to the average value of the previous A cycle values is greater than or equal to the first fluctuation threshold, and after exiting the zero-crossing prediction process, the processor is further configured to output a zero-crossing signal according to the captured actual zero-crossing time.

8. The voltage zero-crossing detection device according to claim 1, wherein, The first time duration is 1 / 8 of the full cycle value, and the second time duration is 3 / 8 of the full cycle value; or, the first time duration is 3 / 16 of the full cycle value, and the second time duration is 5 / 16 of the full cycle value.

9. The zero-crossing voltage detection device according to any one of claims 1 to 8, characterized in that Further includes: A signal conditioning circuit for accessing the AC signal, amplifying or reducing the AC signal and superimposing a bias voltage to convert the AC signal into a conditioned signal above the zero level; A comparator for comparing the conditioned signal with the bias voltage and forming a corresponding output signal; Wherein, the zero-crossing point of the AC signal is captured by detecting the rising edge or falling edge of the output signal of the comparator.

10. A method for detecting the zero-crossing point of voltage, characterized in that, Includes: Obtaining the full cycle value of the AC signal before the captured N-th zero-crossing point, and performing zero-crossing prediction on the (N + 1)-th zero-crossing point; The zero-crossing prediction includes: When capturing the N-th zero-crossing point, start timing; Performing voltage sampling at a first time duration from the N-th zero-crossing point to obtain a first voltage value, and performing voltage sampling at a second time duration from the N-th zero-crossing point to obtain a second voltage value. The first time duration is less than 1 / 4 of the full cycle value, the second time duration is greater than 1 / 4 of the full cycle value, and the difference between 1 / 4 of the full cycle value and the first time duration is equal to the difference between the second time duration and 1 / 4 of the full cycle value; and Obtaining the predicted zero-crossing time of the (N + 1)-th zero-crossing point, where the time duration from the predicted zero-crossing time to the N-th zero-crossing point is (T / 2 + (Ts1 - Ts2) / K1), T is the full cycle value, Ts1 is the first voltage value, Ts2 is the second voltage value, K1 is the first coefficient, and N is a positive integer.

11. A control system, characterized in that, Includes: The voltage zero-crossing detection device according to any one of claims 1 to 9; And A PFC control module is used to control the operation of a PFC circuit. Among them, the PFC control module obtains the predicted zero-crossing moment of the (N + 1)-th zero-crossing point obtained by the voltage zero-crossing detection device, starts the operation associated with the (N + 1)-th zero-crossing point in advance of the predicted zero-crossing moment of the (N + 1)-th zero-crossing point, and completes the operation associated with the (N + 1)-th zero-crossing point at the actual zero-crossing moment of the (N + 1)-th zero-crossing point.

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