Three-phase live wire zero-cross detection chip, circuit and method for alternating-current three-phase four-wire power line

Abstract

The invention relates to an AC three-phase four-wire power line three-phase live wire zero-crossing detection chip, circuit and method. The detection chip comprises a first input pin, a second input pin, a third input pin, a fourth input pin, an output pin, a first Schmitt trigger, a second Schmitt trigger, a third Schmitt trigger, an enabling module, a comparator, a timer, a driver, a controllable switch, a rectifier and a reference voltage module. The comparator is used for comparing the voltage of each phase line with a reference voltage when the voltage of the phase line reaches near a zero point, the timer starts timing when an output signal of the comparator is overturned, and the driver enables the controllable switch to be switched on when the timer starts timing, so that the detection chip outputs a zero-crossing signal; and when the timer finishes timing, the controllable switch is turned off so as to stop the output of the zero-crossing signal.

Description

Technical Field

[0001] The present invention relates to the technical field of zero-crossing detection of live wires, and more particularly to a three-phase live wire zero-crossing detection chip, circuit and method for an AC three-phase four-wire power line. Background Art

[0002] In a three-phase four-wire power meter measurement system, in various application scenarios of an AC three-phase motor, it is necessary to measure the zero-crossing point of the AC power line to implement functions such as phase conversion, calibration, and measurement recognition of corresponding circuits. Currently, to achieve zero-crossing signal detection of an AC three-phase four-wire power line, one method is to use the conduction voltage drop between the base and emitter of multiple triodes or the conduction voltage drop of an optocoupler. This method has defects such as inaccurate zero-crossing voltage detection, large batch discreteness, and high circuit power consumption that cannot meet the grid requirement of 10 mW. Another method is to use a unidirectional zero-crossing detection circuit. Although this method uses a mature unidirectional zero-crossing detection chip, in a three-phase power system, three unidirectional zero-crossing detection circuits are required to implement the three-phase unidirectional zero-crossing detection function, and six unidirectional zero-crossing detection circuits are required to implement the three-phase bidirectional zero-crossing detection function for bidirectional zero-crossing detection. It has defects such as a large PCB board design area, high circuit complexity, and high production and manufacturing costs. Summary of the Invention

[0003] The object of the present invention is to provide a three-phase live wire zero-crossing detection chip, circuit and method for an AC three-phase four-wire power line to overcome the above technical defects.

[0004] On the one hand, the present invention provides an AC three-phase four-wire power line three-phase live wire zero-crossing detection chip, comprising: a first input pin, a second input pin, a third input pin, a fourth input pin, an output pin, a first Schmitt trigger, a second Schmitt trigger, a third Schmitt trigger, an enable module, a comparator, a timer, a driver, a controllable switch, a rectifier and a reference voltage module. The input end of the first Schmitt trigger is connected to the first input pin, the input end of the second Schmitt trigger is connected to the second input pin, the input end of the third Schmitt trigger is connected to the third input pin. The output ends of the first Schmitt trigger, the second Schmitt trigger and the third Schmitt trigger are all connected to the enable module and the timer. One of the first input pin, the second input pin and the third input pin is connected to one of the positive input terminal and the negative input terminal of the comparator, and the other of the positive input terminal and the negative input terminal of the comparator is connected to the reference voltage module. The enable terminal of the comparator is connected to the enable module. The output end of the comparator is connected to the timer or simultaneously connected to the timer and the driver. The timer is connected to the driver. The controllable switch comprises a control end, a first connection end and a second connection end. The control end is connected to the driver, the first connection end is grounded, and the second connection end is connected to the output end of the rectifier. The output end of the rectifier is connected to the fourth input pin. The input end of the rectifier is respectively connected to the first input pin, the second input pin and the third input pin. The output pin is grounded; The first input pin is used to connect to the first phase wire, the second input pin is used to connect to the second phase wire, and the third input pin is used to connect to the third phase wire; the first Schmitt trigger is set to trigger when the voltage of the first phase wire reaches a preset condition and output a first trigger signal; the second Schmitt trigger is set to trigger when the voltage of the second phase wire reaches a preset condition and output a second trigger signal; the third Schmitt trigger is set to trigger when the voltage of the third phase wire reaches a preset condition and output a third trigger signal; the enable module is set to enable the comparator when receiving the first trigger signal or the second trigger signal or the third trigger signal; when the enable module receives the first trigger signal, the comparator compares the voltage of the first phase wire with the reference voltage provided by the reference voltage module; when the enable module receives the second trigger signal, the comparator compares the voltage of the second phase wire with the reference voltage provided by the reference voltage module; when the enable module receives the third trigger signal, the comparator compares the voltage of the third phase wire with the reference voltage provided by the reference voltage module; the timer is set to wake up the first timing time when receiving the first trigger signal, wake up the second timing time when receiving the second trigger signal, and wake up the third timing time when receiving the third trigger signal; the timer is also set to time for a duration equal to the woken-up timing time when the output signal of the comparator flips; the driver is set to output a first drive signal when the output signal of the comparator flips and output a second drive signal when the timer finishes timing; the first drive signal makes the controllable switch conduct, so that the detection chip outputs a zero-crossing signal; the second drive signal makes the controllable switch turn off to stop the output of the zero-crossing signal.

[0005] Optionally, the first timing time, the second timing time, and the third timing time are different from each other and are all less than half the period duration of the alternating current.

[0006] Optionally, the first timing duration, the second timing duration, and the third timing duration satisfy the following relational expression: T2 = M × T1, T3 = N × T1, where T1 is the first timing duration, T2 is the second timing duration, T3 is the third timing duration, M and N are both real numbers, and 3 > M ≥ 2, N ≥ 3 or 0.33 < M ≤ 0.5, 0 < N < 0.33.

[0007] Optionally, the rectifier includes a first diode, a second diode, and a third diode. The positive electrode of the first diode is connected to the first input pin, the positive electrode of the second diode is connected to the second input pin, and the positive electrode of the third diode is connected to the third input pin. The negative electrodes of the first diode, the second diode, and the third diode are interconnected and form the output terminal of the rectifier.

[0008] Optionally, a voltage stabilizing diode is further included, and the voltage stabilizing diode is disposed between the output terminal of the rectifier and the ground.

[0009] Optionally, a first resistor is further included. One end of the first resistor is connected to the second connection terminal of the controllable switch, and the other end is connected to the output pin.

[0010] Optionally, each Schmidt trigger is set to trigger near the zero point of the single falling edge of the voltage of the corresponding phase line, or near the zero point of the single rising edge, or near the zero points of both the rising edge and the falling edge.

[0011] On the other hand, the present invention provides an AC three-phase four-wire power line three-phase live wire zero-crossing detection circuit, which includes a second resistor, a third resistor, a fourth resistor, an optocoupler module, and the above-mentioned AC three-phase four-wire power line three-phase live wire zero-crossing detection chip. The optocoupler module includes a fifth resistor, a sixth resistor, a first capacitor, a DC power supply, a second capacitor, and an optocoupler. The second resistor is disposed between the first phase line and the first input pin, the third resistor is disposed between the second phase line and the second input pin, and the fourth resistor is disposed between the third phase line and the third input pin; the fifth resistor and the first capacitor are connected in series and disposed between the output pin and the fourth input pin. The light-emitting diode of the optocoupler is connected in parallel with the fifth resistor. The second capacitor is disposed between the collector and the emitter of the triode of the optocoupler, and the sixth resistor is disposed between the DC power supply and the collector of the triode of the optocoupler; the connection end of the second capacitor and the emitter of the triode of the optocoupler is grounded, and both ends of the second capacitor form the output terminal of the optocoupler module.

[0012] Optionally, the third resistor, the fourth resistor, and the fifth resistor are each formed by four resistors connected in series.

[0013] On yet another aspect, the present invention provides an AC three-phase four-wire power line three-phase live wire zero-crossing detection method, which includes the following steps: S10: Provide an AC three-phase four-wire power line three-phase live wire zero-crossing detection chip or the above-mentioned AC three-phase four-wire power line three-phase live wire zero-crossing detection circuit; S20: When the voltage of each phase line reaches near the zero point, the comparator compares the voltage of the phase line with a reference voltage and outputs a comparison signal corresponding to the phase line; S30: The timer starts timing when the comparison signal corresponding to each phase line flips, and the duration is the timing duration corresponding to that phase line; S40: The driver outputs a first drive signal when the comparison signal corresponding to each phase line flips, and outputs a second drive signal when the timer finishes timing; S50: The controllable switch conducts when receiving the first drive signal to output a zero-crossing signal; and turns off when receiving the second drive signal to stop the output of the zero-crossing signal; S60: Determine the phase line where the voltage crosses zero according to the duration of the zero-crossing signal. Description of the Drawings

[0014] Figure 1 It is a schematic structural diagram of an AC three-phase four-wire power line three-phase live wire zero-crossing detection chip according to an embodiment of the present invention; Figure 2 It is a schematic structural diagram of an AC three-phase four-wire power line three-phase live wire zero-crossing detection circuit according to an embodiment of the present invention; Figure 3 It is a waveform diagram of the output voltage of an AC three-phase four-wire power line three-phase live wire zero-crossing detection circuit when the Schmitt trigger is triggered only near the zero point of the falling edge according to an embodiment of the present invention; Figure 4 It is a waveform diagram of the output voltage of an AC three-phase four-wire power line three-phase live wire zero-crossing detection circuit when the Schmitt trigger is triggered only near the zero point of the rising edge according to an embodiment of the present invention; Figure 5 It is a waveform diagram of the output voltage of an AC three-phase four-wire power line three-phase live wire zero-crossing detection circuit when the Schmitt trigger is triggered near both the zero point of the rising edge and the zero point of the falling edge according to an embodiment of the present invention; Figure 6 It is a flowchart of an AC three-phase four-wire power line three-phase live wire zero-crossing detection method according to an embodiment of the present invention. Detailed Embodiments

[0015] The following combines the drawings to give the preferred embodiments of the present invention and describes them in detail.

[0016] As Figure 1As shown in the figure, an AC three-phase four-wire power line three-phase live wire zero-crossing detection chip 100 is provided in an embodiment of the present invention. It includes a first input pin 101, a second input pin 102, a third input pin 103, a fourth input pin 104, an output pin 105, a first Schmitt trigger 106, a second Schmitt trigger 107, a third Schmitt trigger 108, an enable module 109, a comparator 110, a timer 111, a driver 112, a controllable switch 113, a rectifier 114, and a reference voltage module 115. The input end of the first Schmitt trigger 106 is connected to the first input pin 101, the input end of the second Schmitt trigger 107 is connected to the second input pin 102, and the input end of the third Schmitt trigger 108 is connected to the third input pin 103. The output ends of the first Schmitt trigger 106, the second Schmitt trigger 107, and the third Schmitt trigger 108 are all connected to the enable module 109 and the timer 111. The comparator 110 has a positive input terminal, a first negative input terminal, a second negative input terminal, a third negative input terminal, and an enable terminal. The first negative input terminal is connected to the first input pin 101, the second negative input terminal is connected to the second input pin 102, the third negative input terminal is connected to the third input pin 103, the positive input terminal is connected to the reference voltage module 115, and the enable terminal is connected to the enable module 109. The output end of the comparator 110 is connected to the timer 111 or simultaneously connected to the timer 111 and the driver 112. The timer 111 is connected to the driver 112. The controllable switch 113 includes a control terminal, a first connection terminal, and a second connection terminal. The control terminal is connected to the driver 112, the first connection terminal is grounded, and the second connection terminal is connected to the output end of the rectifier 114. The output end of the rectifier 114 is connected to the fourth input pin 104. The input end of the rectifier 114 is respectively connected to the first input pin 101, the second input pin 102, and the third input pin 103. The output pin 105 is grounded; the rectifier 114 is used to rectify the alternating current into direct current for the chip operating voltage. The first input pin 101 is used to be connected to the first phase line LA, the second input pin 102 is used to be connected to the second phase line LB, the third input pin 103 is used to be connected to the third phase line LC. The rectifier 114 is used to convert the alternating current of the three-phase live wires into direct current. The reference voltage module 115 is used as a power supply to supply power to other components (such as the enable module 109, the comparator 110, the timer 111, the driver 112, etc.), and provides a reference voltage to the positive input terminal of the comparator 110; each of the first to third Schmitt triggers is set to trigger when the corresponding phase line voltage reaches a preset condition (for example, drops to near zero and / or rises to near zero), and outputs a trigger signal. The first Schmitt trigger 106 outputs a first trigger signal V A , and the second Schmitt trigger 107 outputs a second trigger signal V B, when the third Schmitt trigger 108 is triggered, it outputs a third trigger signal V C , the enabling module 109 is used to receive the first trigger signal V A , the second trigger signal V B and the third trigger signal V C , and when receiving the first trigger signal V A or the second trigger signal V B or the third trigger signal V C , it enables the comparator 110 (i.e., makes the comparator 110 work); when the enabling module 109 receives the first trigger signal V A , the comparator 110 compares the voltage of the first phase line LA with the reference voltage to output a first comparison signal. When the voltage of the first phase line LA is less than the reference voltage, the first comparison signal is at a high level; otherwise, the first comparison signal is at a low level. When the enabling module 109 receives the second trigger signal V B , the comparator 110 compares the voltage of the second phase line LB with the reference voltage to output a second comparison signal. When the voltage of the second phase line LB is less than the reference voltage, the second comparison signal is at a high level; otherwise, the second comparison signal is at a low level. When the enabling module 109 receives the third trigger signal V C , the comparator 110 compares the voltage of the third phase line LC with the reference voltage to output a third comparison signal. When the voltage of the third phase line LC is less than the reference voltage, the third comparison signal is at a high level; otherwise, the third comparison signal is at a low level. The timer 111 is set to wake up the corresponding timing time when receiving different trigger signals. For example, when receiving the first trigger signal V A , it wakes up the first timing time T1, when receiving the second trigger signal V B , it wakes up the second timing time T2, when receiving the third trigger signal V CWhen the third timing time T3 is awakened; the timer 111 is also set to start timing when the output signal of the comparator 110 flips, and the timing time is the currently awakened timing time. For example, when the first timing time T1 is awakened, the output signal of the comparator 110 flips, then the timer 111 starts timing the first timing time T1. When the second timing time T2 is awakened, the output signal of the comparator 110 flips, then the timer 111 starts timing the second timing time T2. When the third timing time T3 is awakened and the output signal of the comparator 110 flips, then the timer 111 starts timing the third timing time T3; the driver 112 is set to output a first drive signal when the timer 111 starts timing and output a second drive signal when the timer 111 finishes timing. The first drive signal is used to drive the controllable switch 113 to conduct, and the second drive signal is used to drive the controllable switch 113 to turn off; when the controllable switch 113 conducts, the detection chip 110 will output a zero-crossing signal through the output pin 105. When the controllable switch 113 turns off, no zero-crossing signal is output.

[0017] In some embodiments, T1, T2, and T3 are different from each other and are all less than the half-cycle duration of the alternating current. For example, T2 = M×T1 and T3 = N×T1 can be set, where 3 > M ≥ 2, N ≥ 3 or 0.33 < M ≤ 0.5, 0 < N < 0.33. In other embodiments, T1 = T2 = T3 are the same, and three-phase zero-crossing signals can be obtained, but phase line identification is not performed.

[0018] The three-phase live wires of the AC three-phase four-wire power line alternate through zero with a 120-degree difference. When the first phase line LA approaches zero, the first Schmitt trigger 106 issues a first trigger signal V A , the first trigger signal V A causes the enable module 109 to issue an enable signal to enable the comparator 110 to work. The comparator 110 compares the voltage of the first phase line LA with the reference voltage. When the voltage of the first phase line LA continues to drop below the reference voltage or increases above the reference voltage, the output signal of the comparator 110 will flip, thereby triggering the timer 111 to time and triggering the driver 112 to issue a first drive signal to make the controllable switch 113 conduct. After the controllable switch 113 conducts, the detection chip 100 will output a zero-crossing signal. The conduction time of the controllable switch 113 is T1, so the duration of the zero-crossing signal is also T1. That is to say, during the zero-crossing process of the first phase line LA, the detection chip 100 will generate a zero-crossing signal with a duration of T1; similarly, during the zero-crossing processes of the second phase line LB and the third phase line LC, zero-crossing signals with durations of T2 and T3 will be generated respectively. Thus, which phase line passes through zero can be judged by the length of the zero-crossing signal.

[0019] The driver 112 can be selectively connected or not connected to the comparator 110. When connected to the comparator 110, the driver 112 outputs a first drive signal when it determines that the output signal of the comparator 110 has flipped. When not connected to the comparator 110, when the timer 111 starts timing, it sends a timing start signal to the driver 112, causing the driver 112 to output a first drive signal. When the timer 111 finishes timing, the timer 111 sends a timing end signal to the driver 112 to cause the driver 112 to output a second drive signal.

[0020] In some embodiments, the rectifier 114 includes a first diode DA, a second diode DB, and a third diode DC. The positive electrode of the first diode DA is connected to the first input pin 101, the positive electrode of the second diode DB is connected to the second input pin 102, and the positive electrode of the third diode DC is connected to the third input pin 103. The negative electrodes of the diodes DA, DB, and DC are connected to each other and form the output terminal of the rectifier 114. The diodes DA, DB, and DC are used to implement half-wave rectification and can therefore also be referred to as half-wave rectifier tubes. The rectifier 114 can also be implemented in other ways, such as using a triode with its base and emitter connected together, or using the parasitic diode of a transistor, etc.

[0021] The reference voltage module 115 is a conventional design of the chip, and its specific implementation method is not described in detail here.

[0022] It can be understood that the comparator 110 can also be set to have three non-inverting input terminals and one inverting output terminal. The inverting output terminal is connected to the reference voltage, and the three non-inverting input terminals are respectively connected to the output terminals of three Schmitt triggers.

[0023] In some embodiments, the detection chip 100 may further include a zener diode ZD, which is disposed between the output terminal of the rectifier 114 and the ground, and is used to clamp the output voltage of the rectifier to prevent damage to the subsequent circuit components.

[0024] In some embodiments, the detection chip 110 further includes a first resistor R1. One end of the first resistor R1 is connected to the second connection terminal of the controllable switch 113, and the other end is connected to the output pin 105. The first resistor R1 is used to limit the current.

[0025] The controllable switch 113 can be an NMOS transistor, a PMOS transistor, or any other suitable switch. When the controllable switch 113 is an NMOS transistor, the first drive signal is a high level, and the second drive signal is a low level.

[0026] The Schmitt trigger can be set to trigger near the zero point of a single falling edge, or near the zero point of a single rising edge, or near the zero point of both the rising edge and the falling edge as needed.

[0027] Comparator 110 can be set to distinguish each phase line LA, LB, and LC according to the input source. The output of comparator 110 can be directly connected to the pulse generation module, so that the pulse generation module generates pulse signals with durations of T1, T2, and T3, that is, the same three-phase zero-crossing signals are obtained.

[0028] Driver 112 may include a current-limiting resistor and a short-circuit switch. The current-limiting resistor is disposed between the second connection end of the controllable switch 113 and the output pin 105. The short-circuit switch is connected to the current-limiting resistor and is used to switch and short-circuit a part of the current-limiting resistor.

[0029] As Figure 2 shown, an embodiment of the present invention further provides a three-phase live wire zero-crossing detection circuit for an AC three-phase four-wire power line, which includes the detection chip 100 as described in the above embodiment, and further includes a second resistor R2, a third resistor R3, a fourth resistor R4, and an optocoupler module. The optocoupler module includes a fifth resistor R5, a sixth resistor R6, a first capacitor C1, a DC power supply VDD, a second capacitor C2, and an optocoupler OPTO. The second resistor R2 is disposed between the first phase line LA and the first input pin 101. The third resistor R3 is disposed between the second phase line LB and the second input pin 102. The fourth resistor R4 is disposed between the third phase line LC and the third input pin 103. The second resistor R2, the third resistor R3, and the fourth resistor R4 are used to limit the maximum current flowing to the detection chip 100 and perform voltage division to prevent the zener diode ZD from being damaged and provide sufficient energy for the circuit to use. The fifth resistor R5 and the first capacitor C1 are connected in series and disposed between the output pin 105 and the fourth input pin 104. The light-emitting diode of the optocoupler OPTO is connected in parallel with the fifth resistor R5. The second capacitor C2 is disposed between the collector and the emitter of the triode of the optocoupler. The sixth resistor R6 is disposed between the DC power supply VDD and the collector of the triode of the optocoupler OPTO. The connection end of the second capacitor C2 and the emitter of the triode of the optocoupler OPTO is grounded. Both ends of the second capacitor C2 form the output end of the optocoupler module (which is also the output end of the detection circuit), and the output voltage is V OUT .

[0030] The detection principle of the detection circuit according to the embodiment of the present invention is as follows: Taking the Schmitt trigger configured as a single falling-edge zero-point additional trigger as an example, the trigger voltage of the Schmitt trigger is 3V. Whenever the phase line voltage drops to 3V, a trigger signal will be issued, and the reference voltage of the comparator 110 is set to 1V. As described above, when the detection chip 100 passes through zero for different phase lines, zero-crossing signals with different durations will be output. The zero-crossing signals will cause the optocoupler OPTO to obtain a light-emitting current and transmit the zero-crossing signals to the secondary. Therefore, the waveform of the output voltage V OUT is as Figure 3As shown, after the waveform of the voltage of the first phase line LA changes from the positive semi-axis to the negative semi-axis and passes through the vicinity of the zero point, the detection circuit outputs a low-level voltage with a duration of T1, and then recovers to a high-level voltage; then after the waveform of the voltage of the second phase line LB changes from the positive semi-axis to the negative semi-axis and passes through the zero point, the detection circuit outputs a low-level voltage with a duration of T2, and then recovers to a high-level voltage; then after the waveform of the voltage of the third phase line LC changes from the positive semi-axis to the negative semi-axis and passes through the zero point, the detection circuit outputs a low-level voltage with a duration of T3, and then recovers to a high-level voltage; this cycle is repeated in each cycle of the AC three-phase electricity, and the phase line that has passed zero can be determined by the duration of the low-level voltage of the output voltage VOUT of the detection circuit.

[0031] The output pin 105 of the detection chip 100 has at least two functions. The first function is to charge the first capacitor C1 through the output pin 105, which serves as the power supply end for other components of the chip except the rectifier 114 and the Zener diode ZD; the second function is to connect the cathode of the light-emitting diode of the optocoupler OPTO to drive the optocoupler module.

[0032] It should be noted that, since the voltage VCC of the output pin 105 is the highest during the time when the controllable switch 113 is just turned on, the current flowing through the first resistor R1 inside the chip is the largest, which can quickly pull down the output, sufficiently light up the light-emitting diode of the optocoupler OPTO, and quickly transmit the zero-crossing signal to the secondary, and then the discharge current decreases linearly with VCC to maintain the signal. In this way, while ensuring that the zero-crossing signal can be transmitted to the secondary of the optocoupler module, the energy storage of the first capacitor C1 can be used as much as possible to extend the discharge time of the first capacitor C1, avoiding the situation that the first capacitor C1 cannot provide enough light-emitting current for the optocoupler due to insufficient energy storage, thereby causing the zero-crossing signal transmission failure and the zero-crossing signal detection result error.

[0033] It should be noted that T1, T2, and T3 should not be too short. If they are too short, the zero-crossing signal will end before the output is pulled low, and it will be impossible to quickly transmit the zero-crossing signal to the secondary and reduce the error between the zero-crossing signal detected at the output end of the optocoupler module and the actual zero-crossing point of the alternating current; the zero-crossing signal duration T1, T2, and T3 should not be too long. If they are too long, too much charge stored on the first capacitor C1 will be consumed, resulting in the timing not being over, and the charge on the first capacitor C1 is insufficient to provide sufficient light-emitting current for the optocoupler, which will cause the zero-crossing signal transmission to fail and the zero-crossing signal detection result to be erroneous.

[0034] The Schmitt trigger can also be set to trigger near the zero point of a single rising edge or trigger near the zero point of both the rising edge and the falling edge. The waveforms of the output voltage VOUT are as follows: Figure 4and Figure 5 as shown Figure 5 The difference between Figure 3 and Figure 4 is that Figure 5 has six zero-crossing signals within one AC cycle, while Figure 3 and Figure 4 only have three zero-crossing signals within one AC cycle

[0035] It should be noted that Figure 3 、 Figure 4 and Figure 5 are only for clearly showing the waveforms of each signal, and there is no any exemplary limitation on the proportion of the width of each signal waveform in the half cycle of the alternating current

[0036] In some embodiments, the second resistor R2 can be formed by four resistors connected in series, and the resistance values of the four resistors are all 750 kΩ. The third resistor R3 and the fourth resistor R4 can also be formed by four resistors with a resistance value of 750 kΩ connected in series; the resistance value of the fifth resistor R5 is 4.7 kΩ, and the resistance value of the sixth resistor R6 is 10 kΩ; the capacitance value of the first capacitor C1 is 1 μF / 16V, and the capacitance value of the second capacitor C2 is 1 nF / 16V

[0037] As Figure 6 shown, the embodiment of the present invention also provides a method for detecting the zero-crossing of three-phase live wires of an AC three-phase four-wire power line, which includes the following steps S10: Provide an AC three-phase four-wire power line three-phase live wire zero-crossing detection chip or circuit as described in the above embodiment S20: When the voltage of each phase line reaches near zero, the comparator 110 compares the voltage of the phase line with the reference voltage and outputs a comparison signal corresponding to the phase line S30: The timer 111 starts timing when the comparison signal corresponding to each phase line flips, and the duration is the timing duration corresponding to the phase line S40: The driver 112 outputs a first drive signal when the comparison signal corresponding to each phase line flips, and outputs a second drive signal when the timer 111 ends timing S50: The controllable switch 113 conducts when receiving the first drive signal to output a zero-crossing signal; and turns off when receiving the second drive signal to stop the output of the zero-crossing signal S60: Judge the phase line where the voltage crosses zero according to the duration of the zero-crossing signal (that is, judge which phase line's voltage crosses zero)

[0038] Based on the generation of the zero-crossing signal, the voltage zero-crossing point can also be determined. After the zero-crossing signal is generated, it indicates that the voltage of a certain phase line is about to cross zero, which is beneficial for other circuits to detect the true zero-crossing point in advance. For example, after receiving the zero-crossing signal, the zero-crossing detection circuit starts to detect the voltage, so as to measure the true zero-crossing point of the voltage.

[0039] The embodiments of the present invention have the following beneficial effects: 1. Anticipate in advance the determination of the zero-crossing points of the three-phase live wires of three-phase four-wire alternating current, and generate a zero-crossing signal in advance for the detection device, so that there is time to prepare for the next action, and the next action can be truly realized at the zero-crossing moment; 2. During a period at the beginning of the zero-crossing signal, a relatively large conduction current is provided to the controllable switch 113, so that the zero-crossing signal can be quickly transmitted through the optocoupler, strengthening the reliability of the zero-crossing signal transmission; 3. By comparing the phase line voltage with the precise reference voltage, the zero-crossing signal has high accuracy and good consistency, further improving the reliability and avoiding the situation that the zero-crossing signal is inaccurate due to parameter drift of discrete devices; 4. Judge whether it is the phase line LA, LB or LC that crosses zero by the width (i.e., the duration) of the zero-crossing signal. The width of the zero-crossing signal can be precisely controlled by a timer, with high accuracy, good mass production consistency, and a set of circuits realizing the functions of traditional three sets of circuits, reducing the system cost and the complexity of PCB (printed circuit board) wiring; 5. The three-phase live wire zero-crossing detection chip for three-phase four-wire power line only has five pins, and only one external capacitor needs to be added to the three-phase four-wire power line three-phase zero-crossing detection circuit. The circuit structure is simple, further reducing the complexity of PCB wiring; 6. Through the current-limiting and voltage-dividing resistors R2, R3 and R4, the three-phase live wire zero-crossing detection circuit for three-phase four-wire power line can meet the power consumption requirements of the power grid.

[0040] The above-mentioned are only the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. Various changes can be made to the above embodiments of the present invention. That is, all simple, equivalent changes and modifications made according to the claims and the content of the specification of the present invention application fall within the scope of the claims of the present invention patent. The content not described in detail in the present invention is all conventional technical content.

Claims

1. An AC three-phase four-wire power line three-phase live line zero-crossing detection chip, characterized in that: The invention comprises a first input pin, a second input pin, a third input pin, a fourth input pin, an output pin, a first Schmitt trigger, a second Schmitt trigger, a third Schmitt trigger, an enabling module, a comparator, a timer, a driver, a controllable switch, a rectifier and a reference voltage module, wherein the input end of the first Schmitt trigger is connected to the first input pin, the input end of the second Schmitt trigger is connected to the second input pin, the input end of the third Schmitt trigger is connected to the third input pin, the output ends of the first Schmitt trigger, the second Schmitt trigger and the third Schmitt trigger are all connected to the enabling module and the timer, the first input pin, the second input pin and the third input pin are connected to the comparator The comparator is connected to one of the positive input terminal and the inverting input terminal, the other of the positive input terminal and the inverting input terminal of the comparator is connected to the reference voltage module, the enable terminal of the comparator is connected to the enable module, the output terminal of the comparator is connected to the timer or is simultaneously connected to the timer and the driver, the timer is connected to the driver, the controllable switch includes a control terminal, a first connection terminal and a second connection terminal, the control terminal is connected to the driver, the first connection terminal is grounded, the second connection terminal is connected to the output terminal of the rectifier, the output terminal of the rectifier is connected to the fourth input pin, the input terminal of the rectifier is respectively connected to the first input pin, the second input pin and the third input pin, and the output pin is grounded.

2. The three-phase live line zero-crossing detection chip for AC three-phase four-wire power line according to claim 1, characterized in that: The first input pin is used to connect to the first phase line, the second input pin is used to connect to the second phase line, and the third input pin is used to connect to the third phase line; the first Schmitt trigger is configured to be triggered when the voltage of the first phase line reaches a preset condition and output a first trigger signal; The second Schmitt trigger is configured to be triggered when the voltage of the second phase line reaches a preset condition, and output a second trigger signal; the third Schmitt trigger is configured to be triggered when the voltage of the third phase line reaches a preset condition, and output a third trigger signal; the enabling module is configured to enable the comparator upon receiving the first trigger signal, the second trigger signal, or the third trigger signal; when the enabling module receives the first trigger signal, the comparator compares the voltage of the first phase line with the reference voltage provided by the reference voltage module; when the enabling module receives the second trigger signal, the comparator compares the voltage of the second phase line with the reference voltage provided by the reference voltage module; When the enabling module receives the third trigger signal, the comparator compares the voltage of the third phase line with the reference voltage provided by the reference voltage module; the timer is configured to wake up the first timing time when the first trigger signal is received, wake up the second timing time when the second trigger signal is received, and wake up the third timing time when the third trigger signal is received; the timer is also configured to perform timing for a duration equal to the awakened timing time when the output signal of the comparator is flipped; the driver is configured to output a first drive signal when the output signal of the comparator is flipped, and output a second drive signal when the timer ends timing; the first drive signal turns on the controllable switch so that the detection chip outputs a zero-crossing signal; The second driving signal turns off the controllable switch to stop outputting the zero-crossing signal.

3. The three-phase live line zero-crossing detection chip for the three-phase four-wire power line of AC according to claim 2 is characterized in that: The first timing time, the second timing time and the third timing time are different from each other and are all shorter than a half-cycle of the alternating current.

4. The three-phase live line zero-crossing detection chip for the three-phase four-wire power line of AC according to claim 3 is characterized in that: The first timing duration, the second timing duration, and the third timing duration satisfy the following relationship: T2=M×T1, T3=N×T1, where T1 is the first timing duration, T2 is the second timing duration, T3 is the third timing duration, M and N are both real numbers, and 3>M≥2, N≥3 or 0.33 <M≤0.5、0<N<0.33。 5. The three-phase live line zero-crossing detection chip for the three-phase four-wire power line of AC according to claim 1, characterized in that: The rectifier includes a first diode, a second diode and a third diode, the anode of the first diode is connected to the first input pin, the anode of the second diode is connected to the second input pin, the anode of the third diode is connected to the third input pin, and the cathodes of the first diode, the second diode and the third diode are connected to each other and form the output end of the rectifier.

6. The three-phase live line zero-crossing detection chip for AC three-phase four-wire power line according to claim 1, characterized in that: It also includes a voltage regulator tube, which is arranged between the output end of the rectifier and the ground.

7. The three-phase live line zero-crossing detection chip for AC three-phase four-wire power line according to claim 1, characterized in that: It also includes a first resistor, one end of which is connected to the second connection end of the controllable switch, and the other end of which is connected to the output pin.

8. The three-phase live line zero-crossing detection chip for the three-phase four-wire power line of AC according to claim 2, characterized in that: Each Schmitt trigger is configured to be triggered near a single falling edge zero point of the voltage of the corresponding phase line, or near a single rising edge zero point, or near both rising and falling edge zero points.

9. An AC three-phase four-wire power line three-phase live line zero-crossing detection circuit, characterized in that: It comprises a second resistor, a third resistor, a fourth resistor, an optical coupling module and an AC three-phase four-wire power line three-phase live line zero-crossing detection chip as described in any one of claims 1 to 8, wherein the optical coupling module comprises a fifth resistor, a sixth resistor, a first capacitor, a DC power supply, a second capacitor and an optical coupling, wherein the second resistor is arranged between the first phase line and the first input pin, the third resistor is arranged between the second phase line and the second input pin, and the fourth resistor is arranged between the third phase line and the third input pin; the fifth resistor and the first capacitor are connected in series and arranged between the output pin and the fourth input pin, the light-emitting diode of the optical coupling is connected in parallel with the fifth resistor, the second capacitor is arranged between the collector and the emitter of the transistor of the optical coupling, and the sixth resistor is arranged between the DC power supply and the collector of the transistor of the optical coupling; the connection end between the second capacitor and the emitter of the transistor of the optical coupling is grounded, and the two ends of the second capacitor form the output end of the optical coupling module.

10. A method for detecting zero crossing of three-phase live wire of an AC three-phase four-wire power line, characterized in that: The following steps are involved: S10: Provide an AC three-phase four-wire power line three-phase live line zero-crossing detection chip as described in any one of claims 1 to 8 or an AC three-phase four-wire power line three-phase live line zero-crossing detection circuit as described in claim 9; S20: When the voltage of each phase line reaches near zero, the comparator compares the voltage of the phase line with the reference voltage and outputs a comparison signal corresponding to the phase line; S30: the timer starts timing when the comparison signal corresponding to each phase line flips, and the duration is the timing duration corresponding to the phase line; S40: The driver outputs a first drive signal when the comparison signal corresponding to each phase line is flipped, and outputs a second drive signal when the timer ends; S50: the controllable switch is turned on when receiving the first driving signal to output the zero-crossing signal; and is turned off when receiving the second driving signal to stop outputting the zero-crossing signal; S60: Determine the phase line whose voltage crosses zero according to the duration of the zero-crossing signal.

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