A safety protection circuit based on photovoltaics

Abstract

The invention discloses a photovoltaic-based safety protection circuit, which relates to the field of safety detection. The photovoltaic-based safety protection circuit comprises: a photovoltaic cell module, which is used to output the voltages of the positive and negative electrodes of all photovoltaic cells connected in series to a fault detection module; a fault detection module, which is used to detect whether there is a voltage difference between the positive and negative electrode voltages of all input photovoltaic cells within a light cycle. When there is a voltage difference, it is determined that the photovoltaic cell is not short-circuited; when there is no voltage difference, it is determined that the photovoltaic cell is short-circuited, and the corresponding light-emitting tube emits light for indication; compared with the prior art, the beneficial effects of the invention are as follows: the invention can distinguish whether the photovoltaic cell is blocked or short-circuited by setting the fault detection module, and can timely detect the short-circuit of the photovoltaic cell, so as to avoid the influence of the temperature rise of the photovoltaic panel, the decrease of the power generation efficiency, etc.; the manual detection module is set, which can manually detect whether the light-emitting tube in the fault detection module is abnormal.

Description

Technical Field

[0001] The invention relates to the field of safety detection, and in particular to a photovoltaic-based safety protection circuit. Background Art

[0002] In photovoltaic power generation, photovoltaic cells on photovoltaic panels are connected in series and parallel to increase the output voltage and current, optimize the voltage and current output of the photovoltaic panel, and thus maximize its power output.

[0003] See also Figure 1 In the series connection of photovoltaic cells, a diode is often connected in parallel with the photovoltaic cells to prevent the hot spot effect. The hot spot effect means that in a photovoltaic cell module, if one or some cells are blocked, these cells will not generate current, but will become a load, consuming the energy generated by other cells with light, causing local heating. In severe cases, it may even burn out the cells, reduce the power output of the module, and even cause the module to be scrapped. Therefore, when the battery is blocked, the attached figure becomes Figure 2 As shown, the current is output through the diode, but there is a battery short circuit. At this time, the circuit is as follows Figure 3 As shown, the current is directly output ( Figure 2 , Figure 3 All of them take a single battery being blocked or short-circuited as an example).

[0004] A battery short circuit will cause the temperature of the photovoltaic panel to rise, the power generation efficiency to decrease, etc. When the battery is blocked or short-circuited, the diode impedance is small, the current is similar, and the output voltage and current of the photovoltaic cell change with the light. Therefore, the existing technology is difficult to distinguish whether the battery is blocked or short-circuited, and cannot detect the battery short circuit in time, which needs to be improved. Summary of the invention

[0005] The purpose of the present invention is to provide a photovoltaic-based safety protection circuit to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A photovoltaic-based safety protection circuit, comprising:

[0008] A photovoltaic cell module, used for outputting the voltages of the positive and negative electrodes of all photovoltaic cells connected in series to the fault detection module;

[0009] The fault detection module is used to detect whether there is a voltage difference between the positive and negative voltages of all photovoltaic cells input within a light cycle. If there is a voltage difference, it is determined that the photovoltaic cell is not short-circuited. If there is no voltage difference, it is determined that the photovoltaic cell is short-circuited, and the corresponding light-emitting tube lights up to indicate;

[0010] Manual detection module, used to drive all light-emitting tubes to emit light through manual switches;

[0011] The output end of the photovoltaic cell module is connected to the first input end of the fault detection module, and the output end of the manual detection module is connected to the second input end of the fault detection module.

[0012] As a further solution of the present invention: the photovoltaic cell module includes multiple battery cells, the second end of the previous battery cell is connected to the first end of the next battery cell, the first end of the first battery cell outputs a voltage, and the second end of the last battery cell is grounded. The battery cell includes a first photovoltaic cell and a fifth diode. The negative electrode of the first photovoltaic cell is connected to the positive electrode of the fifth diode, and the positive electrode of the first photovoltaic cell is connected to the negative electrode of the fifth diode.

[0013] As a further solution of the present invention: the fault detection module includes a plurality of fault detection units, different fault detection units receive voltages of positive and negative electrodes of different photovoltaic cells, and the number of the fault detection units is the same as the number of photovoltaic cells connected in series;

[0014] The fault detection unit includes:

[0015] The voltage receiving subunit is used to receive the voltage of the positive electrode and the negative electrode of the corresponding photovoltaic cell. When there is a voltage difference between the positive electrode and the negative electrode of the corresponding photovoltaic cell, the impedance changing subunit is driven to work;

[0016] The impedance changing subunit is used to output a fixed first voltage signal to the light emitting tube indicating subunit when not in operation; and to output an increased second voltage signal to the light emitting tube indicating subunit when in operation;

[0017] The voltage variation subunit is used to gradually increase the voltage of the time voltage signal output to the light-emitting tube indication subunit as time goes by, and after one illumination cycle ends, the time voltage signal is less than the second voltage signal and greater than the first voltage signal;

[0018] The light-emitting tube indicating subunit is used to drive the light-emitting tube to emit light when receiving the first voltage signal output by the impedance changing subunit; and not drive the light-emitting tube to emit light when receiving the second voltage signal output by the impedance changing subunit;

[0019] The input end of the voltage receiving subunit is connected to the output end of the photovoltaic cell module, the output end of the voltage receiving subunit is connected to the input end of the impedance changing subunit, the output end of the impedance changing subunit is connected to the first input end of the light-emitting tube indicating subunit, and the output end of the voltage changing subunit is connected to the second input end of the light-emitting tube indicating subunit.

[0020] As a further solution of the present invention: the voltage receiving subunit includes a first resistor, a first diode, a second resistor, and a first transistor. One end of the first resistor is connected to the positive electrode of the corresponding photovoltaic cell, the other end of the first resistor is connected to the positive electrode of the first diode, and the negative electrode of the first diode is connected to the negative electrode of the corresponding photovoltaic cell. When the first diode is working and emitting light, it only illuminates the base of the first transistor. The first diode is a light-emitting diode, and the first transistor is a photosensitive transistor. The collector of the first transistor is connected to one end of the second resistor, and the other end of the second resistor is connected to the power supply voltage. The emitter of the first transistor is connected to the impedance change subunit.

[0021] As a further solution of the present invention: the impedance change subunit includes a fifth resistor, a sixth resistor, a seventh resistor, a second MOS tube, a first capacitor, a third resistor, a fourth resistor, and a first thyristor, one end of the third resistor is connected to the power supply voltage, the other end of the third resistor is connected to the positive electrode of the first thyristor, the negative electrode of the first thyristor is connected to one end of the fourth resistor, the G electrode of the second MOS tube, the other end of the fourth resistor is grounded, the control electrode of the first thyristor is connected to the output end of the voltage receiving subunit, one end of the fifth resistor is connected to one end of the sixth resistor and the power supply voltage, the other end of the fifth resistor is connected to the D electrode of the second MOS tube, the S electrode of the second MOS tube is connected to one end of the first capacitor, the other end of the sixth resistor, one end of the seventh resistor, and the first input end of the light-emitting tube indication subunit, the other end of the first capacitor is grounded, and the other end of the seventh resistor is grounded.

[0022] As a further solution of the present invention: the voltage change subunit includes an eighth resistor, a first potentiometer, and a second capacitor, one end of the eighth resistor is connected to the power supply voltage, the other end of the eighth resistor is connected to one end of the first potentiometer, the other end of the first potentiometer is connected to one end of the second capacitor and the second input end of the light-emitting tube indication subunit, and the other end of the second capacitor is grounded.

[0023] As a further solution of the present invention: the light-emitting tube indicator subunit includes a first amplifier, a ninth resistor, and a second diode. The in-phase end of the first amplifier is connected to the output end of the voltage change subunit, the inverting end of the first amplifier is connected to the output end of the impedance change subunit, the output end of the first amplifier is connected to one end of the ninth resistor, the other end of the ninth resistor is connected to the positive electrode of the second diode, and the negative electrode of the second diode is grounded.

[0024] As a further solution of the present invention: the manual detection module includes a tenth resistor, an eleventh resistor, a first switch, and a MOS tube unit. The MOS tube unit is composed of multiple MOS tubes connected in parallel. The number of MOS tubes in the MOS tube unit is the same as the number of fault detection units. One end of the tenth resistor is connected to the power supply voltage, the other end of the tenth resistor is connected to the D poles of all MOS tubes in the MOS tube unit, the S poles of different MOS tubes in the MOS tube unit are respectively connected to the corresponding fault detection units (the second input end of the light-emitting tube indication subunit), the G poles of all MOS tubes in the MOS tube unit are connected to one end of the first switch, the other end of the first switch is connected to one end of the eleventh resistor, and the other end of the eleventh resistor is connected to the power supply voltage.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention can distinguish whether the photovoltaic cell is blocked or short-circuited by setting a fault detection module, and promptly detect the short-circuit of the photovoltaic cell to avoid the effects of the photovoltaic panel temperature rising, the power generation efficiency decreasing, etc.; the manual detection module set up can manually detect whether the light-emitting tube in the fault detection module is abnormal. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Circuit diagram for photovoltaic cells connected in series.

[0027] Figure 2 This is the circuit diagram when there is a shaded cell in the photovoltaic cell series connection.

[0028] Figure 3 This is a circuit diagram when there is a short circuit in the photovoltaic cells in series.

[0029] Figure 4 The schematic diagram of a photovoltaic-based safety protection circuit.

[0030] Figure 5 The schematic diagram of a photovoltaic-based safety protection circuit. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0032] See also Figure 4 , a photovoltaic-based safety protection circuit, comprising:

[0033] Photovoltaic cell module 1, used to output the voltages of the positive and negative electrodes of all photovoltaic cells connected in series to the fault detection module 2;

[0034] Fault detection module 2 is used to detect whether there is a voltage difference between the positive and negative voltages of all photovoltaic cells input within a light cycle. If there is a voltage difference, it is determined that the photovoltaic cell is not short-circuited. If there is no voltage difference, it is determined that the photovoltaic cell is short-circuited, and the corresponding light-emitting tube lights up to indicate;

[0035] Manual detection module 3, used to drive all light-emitting tubes to emit light through manual switches;

[0036] The output end of the photovoltaic cell module 1 is connected to the first input end of the fault detection module 2 , and the output end of the manual detection module 3 is connected to the second input end of the fault detection module 2 .

[0037] In this example: See Figure 5 The photovoltaic cell module 1 includes multiple battery cells, the second end of the previous battery cell is connected to the first end of the next battery cell, the first end of the first battery cell outputs a voltage, and the second end of the last battery cell is grounded. The battery cell includes a first photovoltaic cell E1 and a fifth diode D5. The cathode of the first photovoltaic cell E1 is connected to the anode of the fifth diode D5, and the anode of the first photovoltaic cell E1 is connected to the cathode of the fifth diode D5.

[0038] Figure 5 There are three battery units arranged in the circuit, and there are three common points A1, A2, and A3. For example, when the first photovoltaic cell E1 generates electricity, the voltages at the common points A1 and A2 are different. When the first photovoltaic cell E1 does not generate electricity, the voltage difference between the common points A1 and A2 is very small (the first photovoltaic cell E1 is blocked, and there is a voltage difference of the fifth diode D5) or even no voltage difference (the first photovoltaic cell E1 is short-circuited). However, as long as the first photovoltaic cell E1 is not short-circuited, in one illumination cycle (there is a difference in the time when the sun rises and sets in different regions, so a illumination cycle is different according to different regions. Considering the sunlight exposure, a time period when the sunlight shines on more photovoltaic panels can also be selected, such as from 12 am to 3 pm), it will definitely generate electricity (the photovoltaic panels will be placed in areas with good light), and there will be a voltage difference between the common points A1 and A2.

[0039] In another embodiment: Here, three battery cells are used as an example, but the number of battery cells is not limited in practice.

[0040] In this example: See Figure 5 , the fault detection module 2 includes a plurality of fault detection units, different fault detection units receive the voltages of the positive and negative electrodes of different photovoltaic cells, and the number of the fault detection units is the same as the number of photovoltaic cells connected in series;

[0041] The fault detection unit includes:

[0042] The voltage receiving subunit is used to receive the voltage of the positive electrode and the negative electrode of the corresponding photovoltaic cell. When there is a voltage difference between the positive electrode and the negative electrode of the corresponding photovoltaic cell, the impedance changing subunit is driven to work;

[0043] The impedance changing subunit is used to output a fixed first voltage signal to the light emitting tube indicating subunit when not in operation; and to output an increased second voltage signal to the light emitting tube indicating subunit when in operation;

[0044] The voltage variation subunit is used to gradually increase the voltage of the time voltage signal output to the light-emitting tube indication subunit as time goes by, and after one illumination cycle ends, the time voltage signal is less than the second voltage signal and greater than the first voltage signal;

[0045] The light-emitting tube indicating subunit is used to drive the light-emitting tube to emit light when receiving the first voltage signal output by the impedance changing subunit; and not drive the light-emitting tube to emit light when receiving the second voltage signal output by the impedance changing subunit;

[0046] The input end of the voltage receiving subunit is connected to the output end of the photovoltaic cell module 1, the output end of the voltage receiving subunit is connected to the input end of the impedance changing subunit, the output end of the impedance changing subunit is connected to the first input end of the light-emitting tube indicating subunit, and the output end of the voltage changing subunit is connected to the second input end of the light-emitting tube indicating subunit.

[0047] In this example: See Figure 5 The voltage receiving subunit includes a first resistor R1, a first diode D1, a second resistor R2, and a first transistor V1. One end of the first resistor R1 is connected to the positive electrode of the corresponding photovoltaic cell, the other end of the first resistor R1 is connected to the positive electrode of the first diode D1, and the cathode of the first diode D1 is connected to the cathode of the corresponding photovoltaic cell. When the first diode D1 is working and emitting light, it only illuminates the base of the first transistor V1 (without affecting the photosensitive transistors of other voltage receiving subunits). The first diode D1 is a light-emitting diode, the first transistor V1 is a photosensitive transistor, the collector of the first transistor V1 is connected to one end of the second resistor R2, the other end of the second resistor R2 is connected to the power supply voltage VCC, and the emitter of the first transistor V1 is connected to the impedance change subunit.

[0048] Taking the first photovoltaic cell E1 as an example, in a light cycle, if the first photovoltaic cell E1 is not short-circuited, there must be a voltage difference between the common points A1 and A2, so that the first diode D1 is powered on and works, driving the first transistor V1 to turn on, and sending a driving signal to the impedance change sub-unit; on the contrary, when the first photovoltaic cell E1 is short-circuited, there is no voltage difference between the common points A1 and A2 in the entire light cycle, the first diode D1 does not emit light, the first transistor V1 does not work, and no driving signal is sent to the impedance change sub-unit.

[0049] In another embodiment: the power supply voltage VCC is a stable voltage, which can be supplied by a battery, so as to facilitate the installation of the photovoltaic panel for testing of the present invention. It can also be obtained based on the photovoltaic panel, but needs to be stabilized.

[0050] In this example: See Figure 5 The impedance change subunit includes a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, a second MOS tube V2, a first capacitor C1, a third resistor R3, a fourth resistor R4, and a first thyristor Z1. One end of the third resistor R3 is connected to the power supply voltage VCC, the other end of the third resistor R3 is connected to the positive electrode of the first thyristor Z1, the negative electrode of the first thyristor Z1 is connected to one end of the fourth resistor R4, the G electrode of the second MOS tube V2, the other end of the fourth resistor R4 is grounded, the control electrode of the first thyristor Z1 is connected to the output end of the voltage receiving subunit, one end of the fifth resistor R5 is connected to one end of the sixth resistor R6 and the power supply voltage VCC, the other end of the fifth resistor R5 is connected to the D electrode of the second MOS tube V2, the S electrode of the second MOS tube V2 is connected to one end of the first capacitor C1, the other end of the sixth resistor R6, one end of the seventh resistor R7, and the first input end of the light-emitting tube indication subunit, the other end of the first capacitor C1 is grounded, and the other end of the seventh resistor R7 is grounded.

[0051] The driving signal is not input, the first thyristor Z1 is turned off, the second MOS tube V2 is not turned on, the sixth resistor R6 and the seventh resistor R7 divide the voltage, and the voltage on the seventh resistor R7 is the first voltage signal.

[0052] When the driving signal is input, the first thyristor Z1 is turned on and then continues to be turned on, and then the second MOS tube V2 is continuously turned on, so that even after the driving signal stops being input, the second MOS tube V2 is still turned on. At this time, the sixth resistor R6 is connected in parallel, so that the voltage on the seventh resistor R7 increases, and the voltage on the seventh resistor R7 is the second voltage signal at this time.

[0053] In another embodiment, the second MOS tube V2 may be other types of switch tubes, such as a triode, an IGBT tube, etc.

[0054] In this example: See Figure 5 The voltage change subunit includes an eighth resistor R8, a first potentiometer RP1, and a second capacitor C2. One end of the eighth resistor R8 is connected to the power supply voltage VCC, the other end of the eighth resistor R8 is connected to one end of the first potentiometer RP1, the other end of the first potentiometer RP1 is connected to one end of the second capacitor C2 and the second input end of the light-emitting tube indication subunit, and the other end of the second capacitor C2 is grounded.

[0055] The voltage on the second capacitor C2 is used as a time voltage signal. After the power supply voltage VCC is supplied, the power supply voltage VCC charges the second capacitor C2 through the eighth resistor R8 and the first potentiometer RP1. In one light cycle, the second capacitor C2 is continuously charged, and the voltage thereon gradually increases. At the end of one light cycle, the time voltage signal is less than the second voltage signal and greater than the first voltage signal.

[0056] In another embodiment, whether the power supply voltage VCC supplies power can be controlled by light, by setting a photoresistor, and when the sunlight intensity reaches a threshold value, the resistance change of the photoresistor reaches a required value, and the power supply voltage VCC is controlled to supply power, so that the working time of the present invention is consistent with the working time of the photovoltaic panel, reducing power consumption.

[0057] In this example: See Figure 5 The light-emitting tube indicator subunit includes a first amplifier U1, a ninth resistor R9, and a second diode D2. The in-phase end of the first amplifier U1 is connected to the output end of the voltage change subunit, the inverting end of the first amplifier U1 is connected to the output end of the impedance change subunit, the output end of the first amplifier U1 is connected to one end of the ninth resistor R9, the other end of the ninth resistor R9 is connected to the positive electrode of the second diode D2, and the negative electrode of the second diode D2 is grounded.

[0058] When the first photovoltaic cell E1 is normal, before the end of a light cycle, the impedance change subunit always outputs a second voltage signal to the inverting end of the first amplifier U1, and the non-inverting end of the first amplifier U1 is a time voltage signal. The first amplifier U1 outputs a low level and does not drive the second diode D2 to emit light for indication;

[0059] When the first photovoltaic cell E1 is short-circuited, in one illumination cycle, the impedance variation subunit outputs a first voltage signal to the inverting terminal of the first amplifier U1, and the first amplifier U1 outputs a high level to drive the second diode D2 to emit light, indicating that the first photovoltaic cell E1 is short-circuited.

[0060] Similarly, different photovoltaic cells have corresponding fault detection units (light-emitting tube indicator subunits). By observing the light-emitting status of the light-emitting tube, it can be determined which photovoltaic cell is short-circuited.

[0061] In another embodiment: photovoltaic cells are arranged on photovoltaic panels, and the arrangement of photovoltaic cells on the same batch of photovoltaic panels is fixed. Therefore, after the present invention completes the detection of one photovoltaic panel in one light cycle, it can be removed to check another photovoltaic panel; therefore, the positive and negative voltages of the series-connected photovoltaic cells on the photovoltaic panel can be led out through the connecting plate, so that the fault detection module 2 only needs to obtain the positive and negative voltages of the photovoltaic cells through the connecting plate, and the replacement of the photovoltaic panel that needs to be detected is convenient and quick.

[0062] In this example: See Figure 5 The manual detection module 3 includes a tenth resistor R10, an eleventh resistor R11, a first switch S1, and a MOS tube unit. The MOS tube unit is composed of a plurality of MOS tubes connected in parallel. The number of MOS tubes in the MOS tube unit is the same as the number of fault detection units. One end of the tenth resistor R10 is connected to the power supply voltage VCC, the other end of the tenth resistor R10 is connected to the D poles of all MOS tubes in the MOS tube unit, the S poles of different MOS tubes in the MOS tube unit are respectively connected to the corresponding fault detection units (the second input end of the light-emitting tube indication subunit), the G poles of all MOS tubes in the MOS tube unit are connected to one end of the first switch S1, the other end of the first switch S1 is connected to one end of the eleventh resistor R11, and the other end of the eleventh resistor R11 is connected to the power supply voltage VCC.

[0063] Taking the first photovoltaic cell E1 as an example, when the corresponding second diode D2 fails to emit light, it may cause misjudgment. Therefore, a manual detection module 3 is set. After pressing the first switch S1, the third MOS tube V3 in the figure is turned on, and the second capacitor C2 is quickly charged, so that the voltage on the second capacitor C2 is greater than the second voltage signal, which directly causes the first amplifier U1 to output a high level, and the second diode D2 will emit light when it is normal. Before each detection of a photovoltaic cell short circuit in the photovoltaic panel, by pressing the first switch S1, it can be determined whether the light-emitting tubes of all fault detection units are normal.

[0064] In another embodiment: the first switch S1 is manually controlled, or may be voice controlled or other control methods, which are not limited thereto.

[0065] The working principle of the present invention is: the photovoltaic cell module 1 is used to output the voltages of the positive and negative electrodes of all the photovoltaic cells connected in series to the fault detection module 2; the fault detection module 2 is used to detect whether there is a voltage difference between the positive and negative voltages of all the input photovoltaic cells within a light cycle. When there is a voltage difference, it is determined that the photovoltaic cell is not short-circuited; when there is no voltage difference, it is determined that the photovoltaic cell is short-circuited, and the corresponding light-emitting tube lights up for indication; the manual detection module 3 is used to drive all the light-emitting tubes to emit light through a manual switch.

[0066] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered as exemplary and non-restrictive in all respects.

[0067] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A photovoltaic-based safety protection circuit, characterized in that: The photovoltaic-based safety protection circuit includes: A photovoltaic cell module, used for outputting the voltages of the positive and negative electrodes of all photovoltaic cells connected in series to the fault detection module; The fault detection module is used to detect whether there is a voltage difference between the positive and negative voltages of all photovoltaic cells input within a light cycle. If there is a voltage difference, it is determined that the photovoltaic cell is not short-circuited. If there is no voltage difference, it is determined that the photovoltaic cell is short-circuited, and the corresponding light-emitting tube lights up to indicate; Manual detection module, used to drive all light-emitting tubes to emit light through manual switches; The output end of the photovoltaic cell module is connected to the first input end of the fault detection module, and the output end of the manual detection module is connected to the second input end of the fault detection module; The fault detection module includes a plurality of fault detection units, different fault detection units receive voltages of positive and negative electrodes of different photovoltaic cells, and the number of the fault detection units is the same as the number of photovoltaic cells connected in series; The fault detection unit includes: The voltage receiving subunit is used to receive the voltage of the positive electrode and the negative electrode of the corresponding photovoltaic cell. When there is a voltage difference between the positive electrode and the negative electrode of the corresponding photovoltaic cell, the impedance changing subunit is driven to work; The impedance changing subunit is used to output a fixed first voltage signal to the light emitting tube indicating subunit when not in operation; and to output an increased second voltage signal to the light emitting tube indicating subunit when in operation; The voltage variation subunit is used to gradually increase the voltage of the time voltage signal output to the light-emitting tube indication subunit as time goes by, and after one illumination cycle ends, the time voltage signal is less than the second voltage signal and greater than the first voltage signal; The light-emitting tube indicating subunit is used to drive the light-emitting tube to emit light when receiving the first voltage signal output by the impedance changing subunit; and not drive the light-emitting tube to emit light when receiving the second voltage signal output by the impedance changing subunit; The input end of the voltage receiving subunit is connected to the output end of the photovoltaic cell module, the output end of the voltage receiving subunit is connected to the input end of the impedance changing subunit, the output end of the impedance changing subunit is connected to the first input end of the light-emitting tube indicating subunit, and the output end of the voltage changing subunit is connected to the second input end of the light-emitting tube indicating subunit.

2. The photovoltaic-based safety protection circuit according to claim 1, characterized in that: The photovoltaic cell module includes multiple battery cells, the second end of the previous battery cell is connected to the first end of the next battery cell, the first end of the first battery cell outputs a voltage, and the second end of the last battery cell is grounded. The battery cell includes a first photovoltaic cell and a fifth diode. The negative electrode of the first photovoltaic cell is connected to the positive electrode of the fifth diode, and the positive electrode of the first photovoltaic cell is connected to the negative electrode of the fifth diode.

3. The photovoltaic-based safety protection circuit according to claim 1, characterized in that: The voltage receiving subunit includes a first resistor, a first diode, a second resistor, and a first transistor. One end of the first resistor is connected to the positive electrode of the corresponding photovoltaic cell, the other end of the first resistor is connected to the positive electrode of the first diode, and the negative electrode of the first diode is connected to the negative electrode of the corresponding photovoltaic cell. When the first diode is working and emitting light, it only illuminates the base of the first transistor. The first diode is a light-emitting diode, and the first transistor is a photosensitive transistor. The collector of the first transistor is connected to one end of the second resistor, and the other end of the second resistor is connected to the power supply voltage. The emitter of the first transistor is connected to the impedance change subunit.

4. The photovoltaic-based safety protection circuit according to claim 1, characterized in that: The impedance change subunit includes a fifth resistor, a sixth resistor, a seventh resistor, a second MOS tube, a first capacitor, a third resistor, a fourth resistor, and a first thyristor. One end of the third resistor is connected to the power supply voltage, the other end of the third resistor is connected to the positive electrode of the first thyristor, the negative electrode of the first thyristor is connected to one end of the fourth resistor, the G electrode of the second MOS tube, the other end of the fourth resistor is grounded, the control electrode of the first thyristor is connected to the output end of the voltage receiving subunit, one end of the fifth resistor is connected to one end of the sixth resistor and the power supply voltage, the other end of the fifth resistor is connected to the D electrode of the second MOS tube, the S electrode of the second MOS tube is connected to one end of the first capacitor, the other end of the sixth resistor, one end of the seventh resistor, and the first input end of the light-emitting tube indication subunit, the other end of the first capacitor is grounded, and the other end of the seventh resistor is grounded.

5. The photovoltaic-based safety protection circuit according to claim 1, characterized in that: The voltage change subunit includes an eighth resistor, a first potentiometer, and a second capacitor. One end of the eighth resistor is connected to the supply voltage, the other end of the eighth resistor is connected to one end of the first potentiometer, the other end of the first potentiometer is connected to one end of the second capacitor and the second input end of the light-emitting tube indication subunit, and the other end of the second capacitor is grounded.

6. The photovoltaic-based safety protection circuit according to claim 1, characterized in that: The light-emitting tube indicator subunit includes a first amplifier, a ninth resistor, and a second diode. The in-phase end of the first amplifier is connected to the output end of the voltage change subunit, the inverting end of the first amplifier is connected to the output end of the impedance change subunit, the output end of the first amplifier is connected to one end of the ninth resistor, the other end of the ninth resistor is connected to the positive electrode of the second diode, and the negative electrode of the second diode is grounded.

7. The photovoltaic-based safety protection circuit according to any one of claims 3 to 6, characterized in that: The manual detection module includes a tenth resistor, an eleventh resistor, a first switch, and a MOS tube unit. The MOS tube unit is composed of multiple MOS tubes connected in parallel. The number of MOS tubes in the MOS tube unit is the same as the number of fault detection units. One end of the tenth resistor is connected to the power supply voltage, the other end of the tenth resistor is connected to the D poles of all MOS tubes in the MOS tube unit, the S poles of different MOS tubes in the MOS tube unit are respectively connected to the corresponding fault detection units, the G poles of all MOS tubes in the MOS tube unit are connected to one end of the first switch, the other end of the first switch is connected to one end of the eleventh resistor, and the other end of the eleventh resistor is connected to the power supply voltage.

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