Signal circuit, zero cross detection circuit and electronic equipment

Abstract

The invention discloses a signal circuit, a zero-cross detection circuit and electronic equipment, and belongs to the technical field of electronic circuits. The signal circuit comprises a photoelectric coupler; the band gap voltage circuit is configured to generate a compensation signal based on a voltage difference between the two PN junctions under forward bias; the current compensation circuit is electrically connected with the band gap voltage circuit and is configured to provide compensation current based on the compensation signal, and the compensation current and the PN junction voltage difference are in positive correlation; the first end of the switch is electrically connected with the light emitting side of the photoelectric coupler, the second end of the switch is electrically connected with the output end of the current compensation circuit so as to access compensation current, and the switch is switched on when a trigger signal is accessed to the control end; and the signal output circuit is electrically connected with the light receiving side of the photoelectric coupler. A PN junction voltage difference with a positive temperature coefficient is used for compensation, and current with a positive temperature characteristic is provided for the photoelectric coupler to realize temperature compensation, so that the response time of the optical coupler is basically unchanged in a full working temperature range.

Description

Technical Field

[0001] The present application belongs to the technical field of electronic circuits, and in particular relates to a signal circuit, a zero-crossing detection circuit, and an electronic device. Background Art

[0002] Optocouplers (OCs) are commonly used for signal isolation and transmission due to their low cost and mature device applications. Generally, luminous intensity decreases with increasing temperature. This is because higher temperatures increase stray currents within the LED, affecting its luminous efficiency. Therefore, in high-temperature environments, the luminous intensity of the light emitter decreases, which in turn affects the transmission speed of the optical signal. Furthermore, ambient temperature also affects the sensitivity of phototransistors. The sensitivity of phototransistors varies at different temperatures. Increasing temperature leads to a decrease in sensitivity. This is because the conductive band gap of the photosensitive device increases with temperature, resulting in a decrease in photoelectric conversion efficiency. Therefore, in high-temperature environments, the optical receiver requires a stronger input light signal. In summary, the response of an optocoupler is easily affected by temperature: it responds faster at low temperatures and slower at high temperatures. This can easily cause signal delays in signal detection systems, affecting detection accuracy. Summary of the Invention

[0003] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes a signal circuit, a zero-crossing detection circuit, and an electronic device that utilizes the voltage difference between a PN junction to provide a current with a positive temperature characteristic to a photocoupler for temperature compensation, thereby ensuring that the response time of the photocoupler remains essentially unchanged over the entire operating temperature range.

[0004] In a first aspect, the present application provides a signal circuit, comprising:

[0005] Optocoupler;

[0006] a bandgap voltage circuit configured to generate a compensation signal based on a voltage difference between two PN junctions under forward bias;

[0007] a current compensation circuit electrically connected to the bandgap voltage circuit and configured to provide a compensation current based on the compensation signal, wherein the compensation current is positively correlated with the PN junction voltage difference;

[0008] a switch, wherein a first end of the switch is electrically connected to the light-emitting side of the photocoupler, a second end of the switch is electrically connected to the output end of the current compensation circuit to receive the compensation current, and the switch is turned on when a trigger signal is received at the control end;

[0009] The signal output circuit is electrically connected to the light receiving side of the photocoupler.

[0010] According to one embodiment of the present application, a bandgap voltage circuit includes:

[0011] Operational amplifier unit;

[0012] The first current branch includes a first PN junction portion, a first end of the first PN junction portion is electrically connected to the inverting input terminal of the operational amplifier unit, and a second end of the first PN junction portion is electrically connected to the ground node;

[0013] The second current branch includes a first resistor and a second PN junction portion connected in series, one end of the first resistor is electrically connected to the non-inverting input terminal of the operational amplifier unit, and one end of the second PN junction portion is electrically connected to the ground node;

[0014] The output end of the operational amplifier unit is electrically connected to the first current branch and the second current branch respectively, and the first current branch and the second current branch are controlled to have different currents, and the first PN junction portion and the second PN junction portion have different current densities;

[0015] The current compensation circuit is electrically connected to the second current branch to provide a compensation current based on the current flowing through the second PN junction portion.

[0016] According to one embodiment of the present application, the first current branch includes a first MOS transistor, a source of the first MOS transistor is electrically connected to the reference voltage node, a drain of the first MOS transistor is electrically connected to the first end of the first PN junction portion, and a gate of the first MOS transistor is electrically connected to the output end of the operational amplifier unit;

[0017] The second current branch includes a second MOS transistor, a source of the second MOS transistor is electrically connected to the reference voltage node, a drain of the second MOS transistor is electrically connected to one end of the first resistor, and a gate of the second MOS transistor is electrically connected to the output end of the operational amplifier unit;

[0018] The first MOS transistor and the second MOS transistor have different channel current densities.

[0019] According to one embodiment of the present application, the current compensation circuit includes a third MOS transistor, the source of the third MOS transistor is electrically connected to the reference voltage node, the drain of the third MOS transistor is electrically connected to the second end of the switch, and the gate of the third MOS transistor is electrically connected to the output end of the operational amplifier unit.

[0020] According to one embodiment of the present application, the switch includes a fourth MOS transistor, the drain of the fourth MOS transistor is electrically connected to the drain of the third MOS transistor, the source of the fourth MOS transistor is electrically connected to the first end of the light-emitting side of the optocoupler, the gate of the fourth MOS transistor is used to receive a trigger signal, and the second end of the light-emitting side of the optocoupler is electrically connected to the ground node.

[0021] According to one embodiment of the present application, the first PN junction portion includes a first diode unit, an anode side of the first diode unit is electrically connected to the inverting input terminal of the operational amplifier unit, and a cathode side of the first diode unit is electrically connected to the ground node;

[0022] The second PN junction portion includes a second diode unit, an anode side of the second diode unit is electrically connected to one end of the first resistor, and a cathode side of the second diode unit is electrically connected to the ground node.

[0023] According to an embodiment of the present application, the first diode unit and the second diode unit each include at least one diode, and the number of diodes in the first diode unit and the second diode unit is different.

[0024] According to one embodiment of the present application, the signal output circuit includes a second resistor, a first end of the second resistor is electrically connected to the pull-up voltage node, a second end of the second resistor is electrically connected to the light-receiving side of the optocoupler, and is configured to provide an output signal.

[0025] In the second aspect, the present application provides a zero-crossing detection circuit, including a voltage detection circuit and a signal circuit according to the aforementioned embodiment. The voltage detection circuit is electrically connected to the control end of the switch in the signal circuit and is configured to output a trigger signal to the control end of the switch when the amplitude of the target voltage signal is detected to pass through the zero point.

[0026] In a third aspect, the present application provides an electronic device comprising the aforementioned signal circuit, or comprising the aforementioned zero-crossing detection circuit.

[0027] According to the signal circuit, zero-crossing detection circuit and electronic equipment of the present application, a PN junction voltage difference with a positive temperature coefficient is used for compensation. The current compensation circuit can provide the photocoupler with a current with a positive temperature characteristic to achieve temperature compensation, so that the response time of the photocoupler remains basically unchanged within the entire operating temperature range.

[0028] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0030] Figure 1 This is one of the circuit structure diagrams of the signal circuit provided in the embodiment of the present application;

[0031] Figure 2 1 is a schematic diagram of the circuit structure of the bandgap voltage circuit provided in an embodiment of the present application;

[0032] Figure 3 This is the second circuit structure diagram of the signal circuit provided in the embodiment of the present application;

[0033] Figure 4 This is a voltage signal waveform diagram provided by an embodiment of the present application;

[0034] Figure 5 This is an output waveform diagram of a comparator provided in an embodiment of the present application.

[0035] Reference numerals:

[0036] Optocoupler 10, bandgap voltage circuit 20, first current branch 21, first PN junction portion 211, second current branch 22, second PN junction portion 221, current compensation circuit 30, signal output circuit 40, first to fourth MOS transistors M1-M4, first to second resistors R1-R2, first to second comparators A1-A2, first to second diode units D1-D2. DETAILED DESCRIPTION

[0037] The following describes in detail embodiments of the present application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and are not to be construed as limiting the present application.

[0038] In the following description, a "circuit" refers to a conductive loop consisting of at least one element or subcircuit connected electrically or electromagnetically. When an element or circuit is said to be "coupled to" or "connected to" another element, or when an element / circuit is said to be "coupled to" or "connected between" two nodes, it can be directly coupled or connected to the other element or there can be intervening elements. The connection between the elements can be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there are no intervening elements between the two elements.

[0039] In the description, the terms "first," "second," etc. are used to distinguish similar objects, not to describe a particular order or precedence. It should be understood that the numerical descriptors used in this manner are interchangeable where appropriate, so that the embodiments of the present application can be implemented in an order other than that illustrated or described herein, and that the objects distinguished by "first," "second," etc. are generally of a class and do not limit the number of objects; for example, the first object can be one or more. In addition, the term "and / or" in the specification and claims refers to at least one of the connected objects, and the character " / " generally indicates that the objects connected are in an "or" relationship.

[0040] In addition, descriptions with reference to the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the exemplary expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples.

[0041] In reference Figure 1 , Figure 1 The circuit structure of a signal circuit is shown. One embodiment of the present application proposes a signal circuit. In this embodiment, the signal circuit includes an optocoupler 10, a bandgap voltage circuit 20, a current compensation circuit 30, a switch K, and a signal output circuit 40. The bandgap voltage circuit 20 is configured to generate a compensation signal based on the voltage difference between two PN junctions under forward bias; the current compensation circuit 30 is electrically connected to the bandgap voltage circuit 20 and configured to provide a compensation current based on the compensation signal, and the compensation current is positively correlated with the PN junction voltage difference; the first end of the switch K is electrically connected to the light-emitting side of the optocoupler 10, and the second end of the switch K is electrically connected to the output end of the current compensation circuit 30 to receive the compensation current. The switch K is turned on when the control end receives the trigger signal Vf; the signal output circuit 40 is electrically connected to the light-receiving side of the optocoupler 10.

[0042] It is understood that the voltage of a PN junction has a negative temperature characteristic, decreasing as temperature increases, with the specific temperature coefficient being related to the magnitude of the bias current density. Although the voltages of two PN junctions with different current densities change at different rates with temperature, the difference between the two can result in a voltage with a positive temperature coefficient. Therefore, the bandgap voltage circuit 20 can generate a compensation signal based on the voltage difference between the two PN junctions under forward bias.

[0043] The current compensation circuit 30 is used to provide an input current to the optocoupler 10 . The specific current value is generated according to the compensation signal. The provided current is positively correlated with the PN junction voltage difference and also has a positive temperature characteristic, thereby compensating for the temperature effect on the optocoupler 10 .

[0044] The compensation signal can be a current signal or a voltage signal, and can be set as needed. The amplitude of the compensation signal can have a positive correlation with the voltage difference between the two PN junctions, and the compensation current and the compensation signal can also have a positive correlation. Alternatively, the amplitude of the compensation signal can have a negative correlation with the voltage difference between the two PN junctions, and the compensation current and the compensation signal can also have a negative correlation.

[0045] The switch K may be a MOS (Metal Oxide Semiconductor Field Effect Transistor), an IGBT (Insulate-Gate Bipolar Transistor), or a triode.

[0046] The light-emitting side of the optocoupler 10 is typically provided with a light-emitting diode (LED). The first terminal of the switch K is electrically connected to the anode of the LED, and the cathode of the LED can be electrically connected to the ground node. When the switch K is turned on, the current with a positive temperature characteristic provided by the current compensation circuit 30 flows through the LED, causing it to emit light.

[0047] The control terminal of switch K can be electrically connected to a detection circuit at the front end. The detection circuit generates a trigger signal Vf when the detection object meets the corresponding conditions. The switch is turned on when receiving the trigger signal Vf and turned off when not receiving the trigger signal Vf. The trigger signal Vf can be a high-level signal or a low-level signal. The detection circuit can include an overcurrent detection circuit, an overvoltage detection circuit, etc., and the specific configuration can be based on needs and is not limited in this embodiment.

[0048] The signal output circuit 40 outputs a feedback signal based on the response of the light-receiving device on the light-receiving side of the optocoupler 10 to the light-emitting diode, thereby isolating and transmitting the trigger signal Vf to the back-end circuit. The light-receiving device of the optocoupler 10 can function as a switch, and the specific structure of the signal output circuit 40 can be designed based on the characteristics of the switch. For example, the signal output circuit 40 can include a pull-up circuit that controls the pull-up function based on the response of the light-receiving device of the optocoupler 10, thereby outputting or not outputting the feedback signal.

[0049] According to the signal circuit of the present application, by using a PN junction voltage difference with a positive temperature coefficient for compensation, the current compensation circuit can provide the optocoupler 10 with a current with a positive temperature characteristic to achieve temperature compensation, so that the response time of the optocoupler 10 remains basically unchanged within the entire operating temperature range.

[0050] Reference Figure 2 , Figure 2A circuit structure of a bandgap voltage circuit is shown. In some embodiments, the bandgap voltage circuit 20 includes an operational amplifier unit, a first current branch 21, and a second current branch 22. The first current branch 21 includes a first PN junction 211, a first end of the first PN junction 211 being electrically connected to the inverting input terminal of the operational amplifier unit, and a second end of the first PN junction 211 being electrically connected to a ground node. The second current branch 22 includes a first resistor R1 and a second PN junction 221 connected in series, one end of the first resistor R1 being electrically connected to the non-inverting input terminal of the operational amplifier unit, and a second end of the second PN junction 221 being electrically connected to the ground node. The output terminal of the operational amplifier unit is electrically connected to the first current branch 21 and the second current branch 22, respectively, and the first current branch 21 and the second current branch 22 are controlled to have different currents, and the first PN junction 211 and the second PN junction 221 have different current densities. A current compensation circuit 30 is electrically connected to the second current branch 22 to provide a compensation current based on the current flowing through the second PN junction 221.

[0051] The operational amplifier unit may include a first comparator A1, wherein the positive input terminal of the first comparator A1 serves as the positive input terminal of the operational amplifier unit, and the negative input terminal of the first comparator A1 serves as the negative input terminal of the operational amplifier unit. The voltage of the negative input terminal of the first comparator A1 is equal to the voltage V across the first PN junction 211. 211 The voltage V across the first PN junction 221 is equal to the voltage V across the non-inverting input terminal of the first comparator A1. 221 The sum of the voltage across the first resistor R1 and the voltage across the first resistor R1. 211 =V 221 +I2R1, and then we can get: I2=(V 211 -V 221 ) / R1. Wherein, I2 is the current of the second current branch 22, and R1 is the resistance value of the first resistor R1.

[0052] Referring to the above, (V 211 -V 221 ) has a positive temperature characteristic, and the resistance of the first resistor R1 remains unchanged, so I2 also has a positive temperature characteristic. The current compensation circuit 30 converts I2 into an output current and provides it to the optocoupler 10, thereby achieving temperature compensation for the optocoupler 10. The resistance of the first resistor R1 can be used to adjust the compensation coefficient between the current I2 and the temperature, and can be set as required.

[0053] Reference Figure 3 , Figure 3The circuit structure of a signal circuit is shown. As an example, a first current branch 21 includes a first MOS transistor M1, the source of which is electrically connected to the reference voltage node Vdd, the drain of which is electrically connected to the first end of the first PN junction 21, and the gate of which is electrically connected to the output of the operational amplifier unit. A second current branch 22 includes a second MOS transistor M2, the source of which is electrically connected to the reference voltage node Vdd, the drain of which is electrically connected to one end of the first resistor R1, and the gate of which is electrically connected to the output of the operational amplifier unit. The first MOS transistor M1 and the second MOS transistor M2 have different channel current densities.

[0054] The gates of the first MOS transistor M1 and the second MOS transistor M2 are both electrically connected to the output terminal of the first comparator A1, so the gate voltages of the first MOS transistor M1 and the second MOS transistor M2 are the same. Furthermore, because the first MOS transistor M1 and the second MOS transistor M2 have different channel current densities, different currents flow through the first MOS transistor M1 and the second MOS transistor M2, resulting in different currents in the first current branch 21 and the second current branch 22, thereby causing the PN junction voltage difference to have a positive temperature characteristic.

[0055] The operational amplifier unit may include a first comparator A1, with the output of the first comparator A1 serving as the output of the operational amplifier unit. The first MOS transistor M1 and the second MOS transistor M2 may be P-channel MOS transistors. The first MOS transistor M1 and the second MOS transistor M2 may have different channel lengths or widths, thereby having different channel current densities. For example, if the channel size of the first MOS transistor M1 is m times the channel size of the second MOS transistor M2, and the current flowing through the second MOS transistor M2 is I2, then the current flowing through the first MOS transistor M1 is m × I2.

[0056] As an example, the current compensation circuit 30 includes a third MOS transistor M3, the source of the third MOS transistor M3 is electrically connected to the reference voltage node Vdd, the drain of the third MOS transistor M3 is electrically connected to the second end of the switch, and the gate of the third MOS transistor M3 is electrically connected to the output end of the operational amplifier unit.

[0057] The third MOS transistor M3 can also be a P-channel MOS transistor. The gate voltage of the third MOS transistor M3 is also the same as the gate voltage of the second MOS transistor M2. The third MOS transistor M3 and the second MOS transistor M2 form a current mirror structure, and the replication coefficient K is determined by the size ratio between the third MOS transistor M3 and the second MOS transistor M2. The current I3 flowing through the third MOS transistor M3 and the current I2 flowing through the third MOS transistor M3 satisfy the following equation: I3 = K × I2. K can be 1 or a value greater than 1 and can be set according to specific requirements.

[0058] In some embodiments, the switch K includes a fourth MOS transistor M4, a drain of the fourth MOS transistor M4 is electrically connected to the drain of the third MOS transistor M3, a source of the fourth MOS transistor M4 is electrically connected to the first end of the light-emitting side of the photoelectric coupler 10, a gate of the fourth MOS transistor M4 is used to receive the trigger signal Vf, and a second end of the light-emitting side of the photoelectric coupler 10 is electrically connected to the ground node.

[0059] The fourth MOS transistor M4 can be an N-channel MOS transistor, and the trigger signal Vf can be a high-level signal. When the trigger signal is applied to the gate of the fourth MOS transistor M4, the fourth MOS transistor M4 is turned on. The third MOS transistor M3 replicates the current from the second MOS transistor M2 and transmits it to the drain of the fourth MOS transistor M4. The current then flows through the light-emitting side of the photocoupler 10, causing the light-emitting diode to emit light. Because the current provided to the photocoupler 10 has a temperature compensation effect, it can offset the impact of temperature on the light-emitting performance of the light-emitting diode itself.

[0060] As an example, the first PN junction portion 211 includes a first diode unit D1, the anode side of the first diode unit D1 is electrically connected to the inverting input terminal of the operational amplifier unit, and the cathode side of the first diode unit D1 is electrically connected to the ground node; the second PN junction portion 221 includes a second diode unit D2, the anode side of the second diode unit D2 is electrically connected to one end of the first resistor, and the cathode side of the second diode unit D2 is electrically connected to the ground node.

[0061] The first diode unit D1 and the second diode unit D2 are both forward biased, and the voltage at the inverting input terminal of the first comparator A1 is V D1 , the voltage at the non-inverting input of the first comparator A1 is V D2 +I2R1. Combined with the above, we can know that I2=(V D1 -V D2 ) / R1. The currents flowing through the first diode unit D1 and the second diode unit D2 are different in magnitude, so that (V D1 -V D2 ) has a positive temperature coefficient.

[0062] As an example, the first diode unit D1 and the second diode unit D2 each include at least one diode, and the number of diodes in the first diode unit D1 and the second diode unit D2 is different.

[0063] Taking a discrete device as an example, the diode unit may include at least one diode connected in series. For example, the first diode unit D1 may include one diode, and the second diode unit D2 may include n diodes, where n is an integer greater than 1. Taking an integrated circuit as an example, the first diode unit D1 and the second diode unit D2 may have different PN junction sizes. For example, the PN junction size of the second diode unit D2 is n times the PN junction size of the second diode unit D2, where n is a number greater than 1.

[0064] Continue to refer to Figure 3 In some embodiments, the signal output circuit 40 includes a second resistor R2, a first end of the second resistor R2 is electrically connected to the pull-up voltage node, a second end of the second resistor R2 is electrically connected to the light-receiving side of the optocoupler 10, and is configured to provide an output signal.

[0065] It can be understood that when the light receiving side of the photoelectric coupler 10 does not receive light from the light emitting side, the second end of the second resistor R2 outputs a high level, and when the light receiving side of the photoelectric coupler 10 receives light from the light emitting side, the second end of the second resistor R2 outputs a low level.

[0066] In this embodiment, when the trigger signal is a high-level signal, the light-emitting side of the photocoupler 10 emits light, causing the light-receiving side of the photocoupler 10 to be conductive, and the second end of the second resistor R2 outputs a low-level signal. Upon receiving this low-level signal, the back-end circuit determines that the front-end circuit has generated a trigger signal.

[0067] An embodiment of the present application also provides a zero-crossing detection circuit, including a voltage detection circuit and a signal circuit according to the aforementioned embodiment. The voltage detection circuit is electrically connected to the control end of the switch K in the signal circuit and is configured to output a trigger signal to the control end of the switch when the amplitude of the target voltage signal is detected to pass through zero.

[0068] The target voltage signal refers to the voltage signal of the circuit to be detected. For example, the circuit to be detected may be a power supply circuit, etc. The voltage detection circuit can generate a trigger signal when it detects that the voltage is zero.

[0069] As an example, the voltage detection circuit may include a second comparator A2, a non-inverting input terminal of the second comparator A2 is connected to the target voltage signal, and an inverting input terminal of the second comparator A2 is electrically connected to the ground node. Figure 4 and Figure 5 , Figure 4 shows a voltage signal waveform, Figure 5The output waveform of the second comparator is shown in Figure 1. As can be seen from the figure, when the voltage of the target voltage signal is greater than zero, the second comparator A2 outputs a high level to the fourth MOS transistor M4, at which point the photocoupler 10 outputs a low level. When the voltage of the target voltage signal is less than zero, the second comparator A2 outputs a low level to the fourth MOS transistor M4, at which point the photocoupler 10 outputs a high level. The back-end circuit can detect the switching between high and low levels to detect the zero crossing point of the target voltage signal.

[0070] In this embodiment, an optocoupler signal isolation circuit with temperature compensation capability is applied to zero-crossing detection, which improves the response speed of the zero-crossing detection voltage, thereby ensuring the timeliness of the zero-crossing detection.

[0071] An embodiment of the present application further provides an electronic device, comprising the aforementioned signal circuit, or comprising the aforementioned zero-crossing detection circuit.

[0072] The aforementioned signal circuit and / or zero-crossing detection circuit may be formed using discrete components or formed on a chip using semiconductor technology. An electronic device may include a circuit composed of discrete components or a chip having a circuit formed thereon, thereby improving the performance and reliability of the device.

[0073] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and intent of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A signal circuit, characterized in that: include: Optocoupler; a bandgap voltage circuit configured to generate a compensation signal based on a voltage difference between two PN junctions under forward bias; a current compensation circuit, electrically connected to the bandgap voltage circuit and configured to provide a compensation current based on the compensation signal, wherein the compensation current is positively correlated with the voltage difference; a switch, wherein a first end of the switch is electrically connected to the light-emitting side of the photoelectric coupler, a second end of the switch is electrically connected to the output end of the current compensation circuit to receive the compensation current, and the switch is turned on when a trigger signal is received at a control end; The signal output circuit is electrically connected to the light receiving side of the photocoupler.

2. The signal circuit according to claim 1, wherein: The bandgap voltage circuit comprises: Operational amplifier unit; a first current branch, comprising a first PN junction portion, wherein a first end of the first PN junction portion is electrically connected to the inverting input terminal of the operational amplifier unit, and a second end of the first PN junction portion is electrically connected to a ground node; a second current branch, comprising a first resistor and a second PN junction portion connected in series, wherein one end of the first resistor is electrically connected to the non-inverting input terminal of the operational amplifier unit, and one end of the second PN junction portion is electrically connected to a ground node; The output end of the operational amplifier unit is electrically connected to the first current branch and the second current branch respectively, and the first current branch and the second current branch are controlled to have different currents, and the first PN junction and the second PN junction have different current densities; The current compensation circuit is electrically connected to the second current branch to provide a compensation current based on a current flowing through the second PN junction portion.

3. The signal circuit according to claim 2, characterized in that: The first current branch includes a first MOS transistor, a source of the first MOS transistor is electrically connected to a reference voltage node, a drain of the first MOS transistor is electrically connected to a first end of the first PN junction portion, and a gate of the first MOS transistor is electrically connected to an output end of the operational amplifier unit; The second current branch includes a second MOS transistor, a source of the second MOS transistor is electrically connected to the reference voltage node, a drain of the second MOS transistor is electrically connected to one end of the first resistor, and a gate of the second MOS transistor is electrically connected to the output end of the operational amplifier unit; The first MOS transistor and the second MOS transistor have different channel current densities.

4. The signal circuit according to claim 3, characterized in that: The current compensation circuit includes a third MOS transistor, a source of the third MOS transistor is electrically connected to the reference voltage node, a drain of the third MOS transistor is electrically connected to the second end of the switch, and a gate of the third MOS transistor is electrically connected to the output end of the operational amplifier unit.

5. The signal circuit according to claim 4, characterized in that: The switch includes a fourth MOS transistor, a drain of the fourth MOS transistor being electrically connected to the drain of the third MOS transistor, a source of the fourth MOS transistor being electrically connected to a first end of the light-emitting side of the photoelectric coupler, a gate of the fourth MOS transistor being used to receive a trigger signal, and a second end of the light-emitting side of the photoelectric coupler being electrically connected to a ground node.

6. The signal circuit according to claim 3, characterized in that: The first PN junction portion includes a first diode unit, an anode side of the first diode unit is electrically connected to the inverting input terminal of the operational amplifier unit, and a cathode side of the first diode unit is electrically connected to a ground node; The second PN junction portion includes a second diode unit, an anode side of the second diode unit is electrically connected to one end of the first resistor, and a cathode side of the second diode unit is electrically connected to a ground node.

7. The signal circuit according to claim 6, characterized in that: The first diode unit and the second diode unit each include at least one diode, and the number of diodes in the first diode unit and the number of diodes in the second diode unit are different.

8. The signal circuit according to any one of claims 1 to 7, characterized in that: The signal output circuit includes a second resistor, a first end of the second resistor is electrically connected to the pull-up voltage node, a second end of the second resistor is electrically connected to the light-receiving side of the photocoupler, and is configured to provide an output signal.

9. A zero-crossing detection circuit, characterized in that: It comprises a voltage detection circuit and a signal circuit according to any one of claims 1 to 8, wherein the voltage detection circuit is electrically connected to the control end of a switch in the signal circuit and is configured to output the trigger signal to the control end of the switch when the amplitude of the target voltage signal passes through zero.

10. An electronic device, characterized in that: The method comprises the signal circuit according to any one of claims 1 to 8, or comprises the zero-crossing detection circuit according to claim 9.

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