A zero-crossing detection circuit

Abstract

The present invention discloses a zero-crossing detection circuit. The circuit includes a matching unit, a voltage following unit, a signal conditioning unit, a follow-up voltage reference unit and a judgment unit. The output end of the matching unit is connected to the input end of the voltage following unit, the output end of the voltage following unit is connected to the input ends of the signal conditioning unit and the follow-up voltage reference unit, and the output ends of the signal conditioning unit and the follow-up voltage reference unit are connected to the judgment unit. On the one hand, the present invention sets a follow-up voltage reference unit so that when the collected signal is zero, the output will not be triggered incorrectly, thereby avoiding false detection; on the other hand, the matching unit is set to adapt to different types of signals. At the same time, the present invention can also realize the processing of signals of different frequencies, solving the problem of single signal processing in the prior art.

Description

Technical Field

[0001] The invention relates to a zero-crossing detection circuit, belonging to the technical field of electronic circuits. Background Art

[0002] The existing zero-crossing detection circuit uses the method of comparing the input signal with the zero potential signal for detection. This method can only be applied to continuous periodic signals like sine waves. When there is no signal input or the signal input is always near the zero point, the zero-crossing detection circuit will erroneously trigger the output of a series of pulse signals, causing false detection.

[0003] In addition, the existing zero-crossing detection circuits are usually applicable to lower frequencies, generally at the industrial frequency of 50Hz. However, in some special fields, such as wireless communications, radar, laser and other high-speed occasions, ultra-high-speed zero-crossing detection circuits are required, requiring the detection frequency to be between tens of kHz and hundreds of MHz. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a zero-crossing detection circuit.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] According to a first aspect of an embodiment of the present invention, there is provided a zero-crossing point detection circuit, comprising a matching unit, a voltage following unit, a signal conditioning unit, a servo voltage reference unit and a judgment unit, wherein the output end of the matching unit is connected to the input end of the voltage following unit, the output end of the voltage following unit is connected to the input end of the signal conditioning unit and the servo voltage reference unit, and the output end of the signal conditioning unit and the servo voltage reference unit is connected to the judgment unit;

[0007] When the voltage signal converted by the matching unit into the collected analog signal to be detected is 0V or jitters around 0V, the follow-up voltage reference unit outputs a high-level signal to the judgment unit. The judgment unit compares the high-level signal with the voltage signal received from the signal conditioning unit and outputted in phase with the analog signal, and then outputs a low-level signal.

[0008] According to a second aspect of an embodiment of the present invention, there is provided a zero-crossing detection circuit, comprising a matching unit, a voltage following unit, a signal conditioning unit, a servo voltage reference unit and a judgment unit, wherein the output end of the matching unit is connected to the input end of the voltage following unit, the output end of the voltage following unit is connected to the input end of the signal conditioning unit and the servo voltage reference unit, and the output end of the signal conditioning unit and the servo voltage reference unit is connected to the judgment unit;

[0009] When the voltage signal converted by the matching unit into the collected analog signal to be detected is less than 0V, the follow-up voltage reference unit outputs a 0V voltage signal to the judgment unit. The judgment unit compares the 0V voltage signal with the voltage signal received from the signal conditioning unit and consistent with the phase of the analog signal, and then outputs a low-level signal.

[0010] According to a third aspect of an embodiment of the present invention, there is provided a zero-crossing detection circuit, characterized in that it comprises a matching unit, a voltage following unit, a signal conditioning unit, a servo voltage reference unit and a judgment unit, wherein the output end of the matching unit is connected to the input end of the voltage following unit, the output end of the voltage following unit is connected to the input end of the signal conditioning unit and the servo voltage reference unit, and the output end of the signal conditioning unit and the servo voltage reference unit is connected to the judgment unit;

[0011] When the collected analog signal to be detected is converted into a voltage signal by the matching unit and changes from below 0V to above 0V or from above 0V to below 0V, the follow-up voltage reference unit outputs a 0V voltage signal to the judgment unit for a period of time and then outputs a high-level signal. The judgment unit jumps to a high-level signal and then outputs a low-level signal at the moment when the voltage signal received from the signal conditioning unit and outputted in phase with the analog signal passes through zero.

[0012] Preferably, the follow-up voltage reference unit includes a first delay module, a first comparison module and a voltage sorting module, the input end of the first delay module is connected to the output end of the voltage follower unit, the output end of the first delay module is connected to the input end of the first comparison module, the output end of the first comparison module is connected to the input end of the voltage sorting module, and the output end of the voltage sorting module is connected to the input end of the judgment unit.

[0013] Preferably, for the collected analog signal to be detected that is converted into a voltage signal by the matching unit, when zero-point detection is performed during the change from negative voltage to positive voltage signal, the first delay module includes a first diode, a sixth resistor and a first capacitor, the cathode of the first diode is connected to one end of the sixth resistor and the output end of the voltage follower unit, the anode of the first diode is connected to the other end of the sixth resistor and one end of the first capacitor, and the output end of the first delay module is connected to the input end of the first comparison module, and the other end of the first capacitor is grounded.

[0014] Preferably, for the collected analog signal to be detected that is converted into a voltage signal by the matching unit, when zero-point detection is performed during the change from positive voltage to negative voltage signal, the first delay module includes a second diode, an eleventh resistor and a second capacitor, the anode of the second diode is connected to one end of the eleventh resistor and the output end of the voltage follower unit, the cathode of the second diode is connected to the other end of the eleventh resistor and one end of the second capacitor, and the output end of the first delay module is connected to the input end of the first comparison module, and the other end of the second capacitor is grounded.

[0015] Preferably, the first comparison module includes a first comparator, a ninth resistor and a tenth resistor, the non-phase input terminal of the first comparator is connected to the output terminal of the first delay module, the inverting input terminal of the first comparator is connected to one end of the ninth resistor and the tenth resistor, the other ends of the ninth resistor and the tenth resistor are correspondingly connected to the power supply voltage, the power supply terminal of the first comparator is correspondingly connected to the power supply voltage, and the output terminal of the first comparator is connected to the input terminal of the voltage sorting module.

[0016] Preferably, the sorting module includes a seventh resistor and an eighth resistor, one end of the seventh resistor is connected to the output end of the first comparison module, the other end of the seventh resistor is connected to one end of the eighth resistor and the input end of the judgment unit, and the other end of the eighth resistor is connected to the power supply voltage.

[0017] Preferably, the voltage follower unit is implemented using a dedicated voltage follower chip;

[0018] Alternatively, the voltage follower unit includes a second resistor and a first current feedback amplifier, the non-phase input terminal of the first current feedback amplifier is connected to the output terminal of the matching unit, the second resistor is connected in parallel between the inverting input terminal and the output terminal of the first current feedback amplifier, and the power supply terminal of the first current feedback amplifier is correspondingly connected to the power supply voltage.

[0019] Preferably, the signal conditioning unit includes a second current feedback amplifier, a third resistor, a fourth resistor and a fifth resistor, the non-phase input terminal of the second current feedback amplifier is connected to the output terminal of the first current feedback amplifier through the fourth resistor, the inverting input terminal of the second current feedback amplifier is connected to the third resistor and one end of the fifth resistor, the other end of the third resistor is grounded, the other end of the fifth resistor is connected to the output terminal of the second current feedback amplifier, and the power supply terminal of the second current feedback amplifier is correspondingly connected to the power supply voltage.

[0020] The zero-crossing detection circuit provided by the present invention, on the one hand, sets a follow-up voltage reference unit so that when the collected signal is zero, the output will not be erroneously triggered, thereby avoiding false detection; on the other hand, a matching unit is set to adapt to different types of signals. At the same time, the present invention can also process signals of different frequencies, thereby solving the problem that the prior art can only process signals of lower frequencies. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of the structure of a zero-crossing detection circuit provided by an embodiment of the present invention;

[0022] Figure 2 Circuit principle of the zero-crossing detection circuit provided by the embodiment of the present invention Figure 1 ;

[0023] Figure 3 for Figure 1 The waveform diagram of the corresponding position when the provided zero-crossing detection circuit performs zero-crossing detection;

[0024] Figure 4 Circuit principle of the zero-crossing detection circuit provided by the embodiment of the present invention Figure 2 . DETAILED DESCRIPTION

[0025] The technical content of the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0026] like Figure 1 As shown, the zero-crossing detection circuit provided by the embodiment of the present invention includes a matching unit 1, a voltage following unit 2, a signal conditioning unit 3, a follow-up voltage reference unit 4 and a judgment unit 5; the output end of the matching unit 1 is connected to the input end of the voltage following unit 2, the output end of the voltage following unit 2 is connected to the input end of the signal conditioning unit 3 and the follow-up voltage reference unit 4, and the output end of the signal conditioning unit 3 and the follow-up voltage reference unit 4 is connected to the judgment unit 5.

[0027] The matching unit 1 is used to convert various types of collected analog signals that need to be detected by zero point (hereinafter referred to as analog signals to be detected) into standard voltage signals available to the subsequent stage, so that the subsequent stage unit can process them. The matching unit 1 selects corresponding circuits from the current-to-voltage subcircuit, the low-voltage-to-high-voltage subcircuit, the high-voltage-to-low-voltage circuit, the impedance matching subcircuit, and the variable resistor collection subcircuit according to the type of the collected signal, so as to realize the conversion of the collected signal into a standard voltage signal available to the subsequent stage. For example, the high-voltage signal needs to be stepped down, the current signal needs to be converted into a voltage signal, and the sampling resistor needs differential collection, etc.

[0028] In one embodiment of the present invention, it is assumed that the collected analog signal to be detected is a 50 ohm differential voltage signal (eg Figure 3 According to the collected signal Vin), the matching unit 1 can be implemented by using an impedance matching sub-circuit. Figure 2 As shown, when 50 ohm impedance matching is required, the impedance matching subcircuit may include a 50 ohm first resistor R1 and a differential to single-ended amplifier U1, one end of the first resistor R1 is connected to the positive differential voltage signal and the inverting input end of the differential to single-ended amplifier U1, the other end of the first resistor R1 is connected to the negative differential voltage signal and the non-inverting input end of the differential to single-ended amplifier U1, and the power supply end of the differential to single-ended amplifier U1 is correspondingly connected to the power supply voltages VCC and VSS. Among them, the first resistor R1 is used to achieve impedance matching; the differential to single-ended amplifier U1 is used to convert the collected differential voltage signal into a single-ended voltage signal. It should be emphasized that the structure of the impedance matching subcircuit can use different matching methods according to actual needs, which will not be repeated here.

[0029] The voltage follower unit 2 is used to increase the output power of the signal output by the matching unit 1, improve its driving ability, and avoid the problem that the voltage signal output by the matching unit 1 is easily interfered and inconvenient to handle due to insufficient driving power. The voltage follower unit 2 can be implemented using a dedicated voltage follower chip (such as a radio frequency signal amplifier); Figure 2 As shown, the voltage follower unit 2 may also include a second resistor R2 and a first current feedback amplifier U2, the non-phase input terminal of the first current feedback amplifier U2 is connected to the output terminal of the differential-to-single-ended amplifier U1, the second resistor R2 is connected in parallel between the inverting input terminal and the output terminal of the first current feedback amplifier U2, and the power supply terminal of the first current feedback amplifier U2 is correspondingly connected to the power supply voltages VCC and VSS.

[0030] The signal conditioning unit 3 is used to condition the voltage signal output by the voltage following unit 2 to a voltage Vc suitable for the subsequent unit. For example, when the voltage signal output by the voltage following unit 2 is small, in order to enable the judgment unit 5 to better identify the voltage signal, the signal conditioning unit 3 can be used to amplify the voltage signal by a required multiple. Figure 2As shown, the signal conditioning unit 3 includes a second current feedback amplifier U3, a third resistor R3, a fourth resistor R4 and a fifth resistor R5. The non-inverting input terminal of the second current feedback amplifier U3 is connected to the output terminal of the first current feedback amplifier U2 through the fourth resistor R4. The inverting input terminal of the second current feedback amplifier U3 is connected to one end of the third resistor R3 and the fifth resistor R5. The other end of the third resistor R3 is grounded. The other end of the fifth resistor R5 is connected to the output terminal of the second current feedback amplifier U3. The power supply terminal of the second current feedback amplifier U3 is correspondingly connected to the power supply voltage VCC and VSS. Among them, the third resistor R3 and the fifth resistor R5 are used to adjust the amplification factor of the voltage signal output by the voltage follower unit 2. The fourth resistor R4 is used as a matching resistor between the third resistor R3 and the fifth resistor R5, which not only makes the voltage signal output by the voltage follower unit 2 complete (such as Figure 3 The voltage signal Vc) output after being processed by the signal conditioning unit 3 also makes the second current feedback amplifier U3 work more stably. The reason why the signal conditioning unit 3 adopts the second current feedback amplifier is that its time delay is extremely small.

[0031] When there are glitches in the voltage signal output by the voltage follower unit 2, a filtering module (not shown in the figure) can be additionally provided in the signal conditioning unit 3, the input end of the filtering module is connected to the output end of the second current feedback amplifier U3, and the output end of the filtering module is connected to the input end of the judgment unit 5.

[0032] The necessary filtering of the signal is realized by the filtering module to reduce interference. The filtering module can adopt a high-pass filtering or a low-pass filtering subcircuit.

[0033] The follow-up voltage reference unit 4 is used to change the output signal according to the collected analog signal to be detected, so as to avoid outputting an erroneous pulse signal when there is no signal or the signal is always near the zero point during zero-crossing detection, thereby preventing false detection.

[0034] like Figure 2 and Figure 4 As shown, the follow-up voltage reference unit 4 includes a first delay module 41, a first comparison module 42 and a voltage sorting module 43, the input end of the first delay module 41 is connected to the output end of the voltage follower unit 2, the output end of the first delay module 41 is connected to the input end of the first comparison module 42, the output end of the first comparison module 42 is connected to the input end of the voltage sorting module 43, and the output end of the voltage sorting module 43 is connected to the input end of the judgment unit 5.

[0035] According to the voltage signal output by the matching unit 1, when it is necessary to perform zero-crossing detection on the voltage signal during the change from negative voltage to positive voltage, such as Figure 2As shown, the first delay module 41 includes a first diode D1, a sixth resistor R6 and a first capacitor C1, the cathode of the first diode D1 is connected to one end of the sixth resistor R6 and the output end of the first current feedback amplifier U2, the anode of the first diode D1 is connected to the other end of the sixth resistor R6 and one end of the first capacitor C1, and the output end of the first delay module 41 is connected to the input end of the first comparison module 42, and the other end of the first capacitor C1 is grounded.

[0036] According to the voltage signal output by the matching unit 1, when it is necessary to perform zero-crossing detection on the voltage signal during the process of changing from positive voltage to negative voltage, such as Figure 4 As shown, the first delay module 41 includes a second diode D2, an eleventh resistor R11 and a second capacitor C2, the anode of the second diode D2 is connected to one end of the eleventh resistor R11 and the output end of the first current feedback amplifier U2, the cathode of the second diode D2 is connected to the other end of the eleventh resistor R11 and one end of the second capacitor C2, and the output end of the first delay module 41 is connected to the input end of the first comparison module 42, and the other end of the second capacitor C2 is grounded.

[0037] like Figure 2 and Figure 4 As shown, the first comparison module 42 includes a first comparator U4, a ninth resistor R9 and a tenth resistor R10, the non-phase input terminal of the first comparator U4 is connected to the output terminal of the first delay module 41, the inverting input terminal of the first comparator U4 is connected to one end of the ninth resistor R9 and the tenth resistor R10, the other end of the ninth resistor R9 and the tenth resistor R10 is correspondingly connected to the power supply voltage VCC and VSS, the power supply terminal of the first comparator U4 is correspondingly connected to the power supply voltage VCC and VSS, and the output terminal of the first comparator U4 is connected to the input terminal of the voltage sorting module 43.

[0038] like Figure 2 and Figure 4 As shown, the voltage sorting module 43 includes a seventh resistor R7 and an eighth resistor R8, one end of the seventh resistor R7 is connected to the output end of the first comparator U4, the other end of the seventh resistor R7 is connected to one end of the eighth resistor R8 and the input end of the judgment unit 5, and the other end of the eighth resistor R8 is connected to the power supply voltage Vcc.

[0039] For the voltage signal converted by the matching unit 1 into the collected analog signal to be detected, when the zero-crossing detection is performed in the process of changing from negative voltage to positive voltage, the voltage obtained by dividing the ninth resistor R9 and the tenth resistor R10 in the first comparison module 42 is a negative voltage; when the voltage signal output by the matching unit 1 changes from positive voltage to negative voltage (from large to small), the voltage drop at the cathode end of the first diode D1 is less than the voltage drop at the anode end thereof, so that the first diode D1 is turned on, and the capacitance on the first capacitor C1 changes with the input voltage signal. At the same time, the voltage signal output by the matching unit 1 is input to the first comparator U4 through the first diode D1 and the sixth resistor R6 (wherein the voltage flowing through the first diode D 1 is much larger than the voltage signal flowing through the sixth resistor R6), and quickly reaches the voltage-divided value of the ninth resistor R9 and the tenth resistor R10; when the voltage signal output by the matching unit 1 changes from negative voltage to positive voltage, the first diode D1 is not conducting, the sixth resistor R6 and the first capacitor C1 form an RC sub-circuit, and the voltage on the first capacitor C1 decreases slowly, forming a delay effect, that is, after a period of time, the voltage input to the first comparator U4 will reach the voltage-divided value of the ninth resistor R9 and the tenth resistor R10, so that the first comparator U4 outputs a negative voltage signal for a longer time than a positive voltage signal.

[0040] Specifically, Figure 3 As shown, if the voltage signal output by the matching unit 1 is 0V, after passing through the first comparator U4 and the seventh resistor R7 and the eighth resistor R8, the output voltage Vr is a high level; if the voltage signal output by the matching unit 1 is less than 0V, after passing through the first comparator U4 and the seventh resistor R7 and the eighth resistor R8, the output voltage Vr is 0V; if the voltage signal output by the matching unit 1 changes from below 0V to above 0V, due to the existence of the delay of the first delay module 41, after passing through the first comparator U4 and the seventh resistor R7 and the eighth resistor R8, the output voltage Vr is still 0V, and when the delay of the first delay module 41 ends, after passing through the first comparator U4 and the seventh resistor R7 and the eighth resistor R8, the output voltage Vr is a high level. Wherein, according to the power supply voltage VCC, the resistance values ​​of the seventh resistor R7 and the eighth resistor R8 when the output voltage Vr is 0V are pre-calculated.

[0041] For the voltage signal converted by the matching unit 1 from the collected analog signal to be detected, when the zero-crossing detection is performed during the change from positive voltage to negative voltage, the voltage obtained by dividing the ninth resistor R9 and the tenth resistor R10 in the first comparison module 42 is a positive voltage; when the voltage signal output by the matching unit 1 changes from negative voltage to positive voltage, the second diode D2 is turned on, and the capacitance on the second capacitor C2 changes with the input voltage signal. At the same time, the voltage signal output by the matching unit 1 is input to the first comparator U4 through the second diode D2 and the eleventh resistor R11, and quickly reaches the divided voltage value of the ninth resistor R9 and the tenth resistor R10; when the voltage signal output by the matching unit 1 changes from positive voltage to negative voltage, the second diode D2 is not turned on, the eleventh resistor R11 and the second capacitor C2 form an RC sub-circuit, and the voltage on the second capacitor C2 slowly decreases, forming a delay effect, that is, after a period of time, the voltage input to the first comparator U4 will reach the divided voltage value of the ninth resistor R9 and the tenth resistor R10, so that the time for the first comparator U4 to output the positive voltage signal is longer than the time for the negative voltage signal.

[0042] Specifically, if the voltage signal output by the matching unit 1 is 0V, after passing through the first comparator U4 and the seventh resistor R7 and the eighth resistor R8, the output voltage Vr is a high level; if the voltage signal output by the matching unit 1 is less than 0V, after passing through the first comparator U4 and the seventh resistor R7 and the eighth resistor R8, the output voltage Vr is 0V; if the voltage signal output by the matching unit 1 changes from above 0V to below 0V, due to the existence of the delay of the first delay module 41, after passing through the first comparator U4 and the seventh resistor R7 and the eighth resistor R8, the output voltage Vr is still 0V, and when the delay of the first delay module 41 ends, after passing through the first comparator U4 and the seventh resistor R7 and the eighth resistor R8, the output voltage Vr is a high level.

[0043] The judgment unit 5 is used to compare the two signals output by the signal conditioning unit 3 and the follow-up voltage reference unit 4, and then output the required zero-crossing signal. The judgment unit 5 can be implemented by a second comparator. Figure 2 and Figure 4 As shown, the inverting input terminal of the second comparator U5 is connected to the output terminal of the follow-up voltage reference unit 4 (the other end of the seventh resistor R7 and one end of the eighth resistor R8 are connected together as the output terminal of the follow-up voltage reference unit 4), the non-inverting input terminal of the second comparator U5 is connected to the output terminal of the second current feedback amplifier U3, and the power supply terminal of the second comparator U5 is correspondingly connected to the power supply voltage VCC and VSS. The in-phase input terminal of the second comparator U5 inputs a signal that is consistent with the phase of the collected analog signal to be detected, and the inverting input terminal inputs a signal that is consistent with the collected signal and whose zero potential time is slightly later than the zero-crossing time of the collected signal due to the existence of the follow-up voltage reference unit.

[0044] Specifically, Figure 3 As shown, when the voltage Vr output by the follow-up voltage reference unit 4 is high, the voltage Vout output by the second comparator U5 is low; when the follow-up voltage reference unit 4 outputs 0v, the voltage Vout output by the second comparator U5 is low; when the voltage signal output by the matching unit 1 changes from below 0v to above 0v or from above 0v to below 0v, the second comparator U5 jumps to a high level at the moment when the voltage signal passes through zero. When the first delay module 41 ends the delay, the follow-up voltage reference unit 4 outputs a high level, and the voltage Vout output by the second comparator U5 is low.

[0045] To summarize, through the follow-up voltage reference unit 4, when the collected analog signal to be detected is zero or jitters near the zero point, the zero-crossing detection circuit will output a low-level signal to avoid false detection. When the collected signal is not zero and the signal changes from negative voltage to positive voltage, the circuit outputs a rising edge signal.

[0046] In addition, the zero-crossing detection circuit provided by the embodiment of the present invention uses high-speed devices as the corresponding devices of each unit, so that the signal frequency that can be processed by the zero-crossing detection circuit can reach hundreds of MHz at most, solving the problem of low and single frequency use in the prior art. For example, the impedance matching subcircuit of the matching unit 1 can use a differential-to-single-ended high-speed amplifier, the voltage follower unit 2 and the signal conditioning unit can respectively use a high-speed current feedback amplifier, the diode of the first delay module 41 of the follow-up voltage reference unit 4 can use a high-speed diode, the first comparison module 42 of the follow-up voltage reference unit 4 and the comparator of the judgment unit 5 can use a high-speed comparator, and according to the frequency of the required acquisition signal, the parameters of the resistance and capacitance of the first delay module 41 are adjusted to be suitable for signals of different frequencies. Among them, the higher the frequency of the required acquisition signal, the shorter the charging time of the RC subcircuit composed of the resistor and the capacitor in the first delay module 41, and the shorter the delay time of the first delay module 41.

[0047] The zero-crossing detection circuit provided by the present invention, on the one hand, sets a follow-up voltage reference unit so that when the collected signal is zero, the output will not be erroneously triggered, thereby avoiding false detection; on the other hand, a matching unit is set to adapt to different types of signals. At the same time, the present invention can also process signals of different frequencies, thereby solving the problem that the prior art can only process signals of lower frequencies.

[0048] The zero-crossing detection circuit provided by the present invention is described in detail above. For those skilled in the art, any obvious changes made to it without departing from the essence of the present invention will fall within the protection scope of the patent right of the present invention.

Claims

1. A zero-crossing detection circuit, characterized in that It includes a matching unit, a voltage following unit, a signal conditioning unit, a servo voltage reference unit and a judgment unit, wherein the output end of the matching unit is connected to the input end of the voltage following unit, the output end of the voltage following unit is connected to the input ends of the signal conditioning unit and the servo voltage reference unit, and the output ends of the signal conditioning unit and the servo voltage reference unit are connected to the judgment unit; When the voltage signal converted by the matching unit into the collected analog signal to be detected is 0V or fluctuates around 0V, the follow-up voltage reference unit outputs a high-level signal to the judgment unit, and the judgment unit compares the high-level signal with the voltage signal received from the signal conditioning unit and outputted in phase with the analog signal, and then outputs a low-level signal. The follow-up voltage reference unit includes a first delay module, a first comparison module and a voltage sorting module, the input end of the first delay module is connected to the output end of the voltage follower unit, the output end of the first delay module is connected to the input end of the first comparison module, the output end of the first comparison module is connected to the input end of the voltage sorting module, and the output end of the voltage sorting module is connected to the input end of the judgment unit.

2. A zero-crossing detection circuit, characterized in that It includes a matching unit, a voltage following unit, a signal conditioning unit, a servo voltage reference unit and a judgment unit, wherein the output end of the matching unit is connected to the input end of the voltage following unit, the output end of the voltage following unit is connected to the input ends of the signal conditioning unit and the servo voltage reference unit, and the output ends of the signal conditioning unit and the servo voltage reference unit are connected to the judgment unit; When the voltage signal converted by the matching unit into the collected analog signal to be detected is less than 0V, the follow-up voltage reference unit outputs a 0V voltage signal to the judgment unit, and the judgment unit compares the 0V voltage signal with the voltage signal received from the signal conditioning unit and outputted in phase with the analog signal, and then outputs a low-level signal. The follow-up voltage reference unit includes a first delay module, a first comparison module and a voltage sorting module, the input end of the first delay module is connected to the output end of the voltage follower unit, the output end of the first delay module is connected to the input end of the first comparison module, the output end of the first comparison module is connected to the input end of the voltage sorting module, and the output end of the voltage sorting module is connected to the input end of the judgment unit.

3. A zero-crossing detection circuit, characterized in that It includes a matching unit, a voltage following unit, a signal conditioning unit, a servo voltage reference unit and a judgment unit, wherein the output end of the matching unit is connected to the input end of the voltage following unit, the output end of the voltage following unit is connected to the input ends of the signal conditioning unit and the servo voltage reference unit, and the output ends of the signal conditioning unit and the servo voltage reference unit are connected to the judgment unit; When the voltage signal converted by the matching unit to the collected analog signal to be detected changes from below 0V to above 0V or from above 0V to below 0V, the follow-up voltage reference unit outputs a 0V voltage signal to the judgment unit for a period of time and then outputs a high-level signal. The judgment unit jumps to a high-level signal and then outputs a low-level signal at the moment when the voltage signal received from the signal conditioning unit and outputted in phase with the analog signal passes through zero. The follow-up voltage reference unit includes a first delay module, a first comparison module and a voltage sorting module, the input end of the first delay module is connected to the output end of the voltage follower unit, the output end of the first delay module is connected to the input end of the first comparison module, the output end of the first comparison module is connected to the input end of the voltage sorting module, and the output end of the voltage sorting module is connected to the input end of the judgment unit.

4. The zero-crossing detection circuit according to any one of claims 1 to 3, characterized in that: For the collected analog signal to be detected that is converted into a voltage signal through the matching unit, when zero-crossing detection is performed during the change from negative voltage to positive voltage signal, the first delay module includes a first diode, a sixth resistor and a first capacitor, the cathode of the first diode is connected to one end of the sixth resistor and the output end of the voltage follower unit, the anode of the first diode is connected to the other end of the sixth resistor and one end of the first capacitor, and the output end of the first delay module is connected to the input end of the first comparison module, and the other end of the first capacitor is grounded.

5. The zero-crossing detection circuit according to any one of claims 1 to 3, characterized in that: For the collected analog signal to be detected that is converted into a voltage signal through the matching unit, when zero-point detection is performed during the change process of the positive voltage-negative voltage signal, the first delay module includes a second diode, an eleventh resistor and a second capacitor, the anode of the second diode is connected to one end of the eleventh resistor and the output end of the voltage follower unit, the cathode of the second diode is connected to the other end of the eleventh resistor and one end of the second capacitor, and the output end of the first delay module is connected to the input end of the first comparison module, and the other end of the second capacitor is grounded.

6. The zero-crossing detection circuit according to any one of claims 1 to 3, characterized in that: The first comparison module includes a first comparator, a ninth resistor and a tenth resistor, the non-phase input terminal of the first comparator is connected to the output terminal of the first delay module, the inverting input terminal of the first comparator is connected to one end of the ninth resistor and the tenth resistor, the other ends of the ninth resistor and the tenth resistor are correspondingly connected to the power supply voltage, the power supply terminal of the first comparator is correspondingly connected to the power supply voltage, and the output terminal of the first comparator is connected to the input terminal of the voltage sorting module.

7. The zero-crossing detection circuit according to any one of claims 1 to 3, characterized in that: The voltage sorting module includes a seventh resistor and an eighth resistor, one end of the seventh resistor is connected to the output end of the first comparison module, the other end of the seventh resistor is connected to one end of the eighth resistor and the input end of the judgment unit, and the other end of the eighth resistor is connected to the power supply voltage.

8. The zero-crossing detection circuit according to any one of claims 1 to 3, characterized in that: The voltage follower unit is implemented by a dedicated voltage follower chip; Alternatively, the voltage follower unit includes a second resistor and a first current feedback amplifier, the non-phase input terminal of the first current feedback amplifier is connected to the output terminal of the matching unit, the second resistor is connected in parallel between the inverting input terminal and the output terminal of the first current feedback amplifier, and the power supply terminal of the first current feedback amplifier is correspondingly connected to the power supply voltage.

9. The zero-crossing detection circuit according to any one of claims 1 to 3, characterized in that: The signal conditioning unit includes a second current feedback amplifier, a third resistor, a fourth resistor and a fifth resistor. The non-phase input terminal of the second current feedback amplifier is connected to the output terminal of the first current feedback amplifier through the fourth resistor. The inverting input terminal of the second current feedback amplifier is connected to the third resistor and one end of the fifth resistor. The other end of the third resistor is grounded. The other end of the fifth resistor is connected to the output terminal of the second current feedback amplifier. The power supply terminal of the second current feedback amplifier is correspondingly connected to the power supply voltage.

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