Weak light detection circuit and solar power generation system

Abstract

The utility model relates to a kind of weak light detection circuit and solar power generation system, the weak light detection circuit is connected between photovoltaic module and maximum power point tracking module, comprising: load module, relay control module, sampling module, feedback control module and control signal generation module;The load module, the sampling module and the feedback control module are connected between the positive pole and the negative pole of the photovoltaic module;The sampling module is used for sampling sampling voltage indicating ambient light;The control signal generation module is electrically connected with the relay control module, the sampling module and the feedback control module, and is used for controlling the relay control module or the feedback control module to be turned on or turned off based on the sampling voltage and reference voltage.The utility model realizes weak light detection by pure hardware mode, without using external MCU, and circuit is simple, so weak light detection can be completed with low cost and high timeliness.

Description

Technical Field

[0001] This utility model relates to the field of solar power generation, and more specifically, to a low light detection circuit and a solar power generation system. Background Technology

[0002] When the photovoltaic panels of a solar power system are in low light conditions, if the power equipment repeatedly wakes up and powers the connected battery pack, it may deplete the battery pack's power and cause it to crash. Therefore, a low light detection circuit is needed to monitor the photovoltaic output power to prevent the battery pack from being depleted and crashing under low light conditions.

[0003] However, traditional low-light detection circuits generally require additional MCU control circuitry, which not only increases costs but also introduces delays in response time and sensitivity. Furthermore, the multi-level topologies and additional control circuits currently used are both costly and inefficient. Utility Model Content The technical problem to be solved by this utility model is to provide a weak light detection circuit that addresses the above-mentioned deficiencies of the prior art. The circuit is simple and therefore can complete the weak light detection at low cost and with high efficiency.

[0004] The technical solution adopted by this utility model to solve its technical problem is: to construct a weak light detection circuit, which is connected between the photovoltaic module and the maximum power point tracking module, including: a load module, a relay control module, a sampling module, a feedback control module, and a control signal generation module; The load module, the sampling module, and the feedback control module are connected in series between the positive and negative terminals of the photovoltaic module; The relay control module is connected between the positive terminal of the photovoltaic module and the first terminal of the maximum power point tracking module; the negative terminal of the photovoltaic module is connected to the second terminal of the maximum power point tracking module. The sampling module is used to sample the voltage representing ambient light. The control signal generation module is electrically connected to the relay control module, the sampling module, and the feedback control module, and is used to control the relay control module or the feedback control module to be turned on or off based on the sampled voltage and the reference voltage.

[0005] In the weak light detection circuit described in this utility model, the control signal generation module includes a signal amplification unit, a comparator unit, and a latch unit; The signal amplification unit is connected to the sampling module to receive and amplify the sampling voltage; The comparator unit is used to compare the sampled voltage and the reference voltage, and generate a relay control signal and a feedback control signal based on the comparison result; The latch unit is used to latch or output the relay control signal and the feedback control signal.

[0006] The weak light detection circuit of this utility model further includes an over-temperature protection module, the first end of which is connected to the load module, and the second end of which is connected to the signal amplification unit and the comparator unit.

[0007] In the weak light detection circuit of this utility model, the load module includes two dummy loads connected in parallel; the sampling module includes a sampling resistor.

[0008] In the weak light detection circuit of this utility model, the signal amplification unit includes an operational amplifier; the comparator unit includes a comparator, a first diode, and a first resistor; and the latch unit includes a D latch. The inverting input of the operational amplifier is connected to the first terminal of the sampling resistor, the non-inverting input is connected to the second terminal of the sampling resistor, and the output is connected to the inverting input of the comparator. The non-inverting input of the comparator is connected to the positive terminal of the photovoltaic module and the cathode of the first diode, and the anode of the first diode is connected to the negative terminal of the photovoltaic module through the first resistor. The output of the comparator is connected to the D terminal of the D latch. The Q terminal of the D latch is connected to the feedback control module and the relay control module, and the LE terminal is connected to the relay control module.

[0009] In the weak light detection circuit described in this utility model, the feedback control module includes a NAND gate and a first switching transistor; The A terminal of the NAND gate is connected to the first power supply voltage, the B terminal is connected to the Q terminal of the D latch, the power supply terminal is connected to the first power supply voltage, the ground terminal is connected to the negative terminal of the photovoltaic module, and the Y terminal is connected to the control terminal of the first switching transistor. The first terminal of the first switching transistor is connected to the negative terminal of the photovoltaic module, and the second terminal is connected to the non-inverting input terminal of the operational amplifier and the second terminal of the sampling resistor.

[0010] In the weak light detection circuit described in this utility model, the relay control module includes a second switching transistor, a second resistor, a third resistor, a second diode, and a relay; The first terminal of the relay switch is connected to the positive terminal of the photovoltaic module, the second terminal of the relay switch is connected to the first terminal of the maximum power point tracking module, the first terminal of the relay coil is connected to the cathode of the second diode, and the second terminal of the relay coil is connected to the LE terminal of the D latch. The anode of the second diode is connected to the second terminal of the second switching transistor, the control terminal of the second switching transistor is connected to the Q terminal of the D latch via the second resistor, and the first terminal of the second switching transistor is connected to the negative terminal of the photovoltaic module. The third resistor is connected between the negative terminal of the photovoltaic module and the control terminal of the second switching transistor.

[0011] In the weak light detection circuit described in this utility model, the switching transistor is an NMOS transistor, the control terminal of the switching transistor is the gate of the NMOS transistor, the first terminal of the switching transistor is the drain of the NMOS transistor, and the second terminal of the switching transistor is the source of the NMOS transistor; the NAND gate is an SN74LVC1G00DBVR NAND gate; and the D latch is an SN74LVC1G373DBVR latch.

[0012] In the weak light detection circuit of this utility model, the over-temperature protection module includes a third diode, a fourth resistor and an NTC resistor. The first end of the NTC resistor is connected to the first power supply voltage, and the second end is connected to the anode of the third diode through the fourth resistor. The cathode of the third diode is connected to the inverting input terminal of the comparator.

[0013] Another solution adopted by this utility model to solve its technical problem is to construct a solar power generation system, including a photovoltaic module, a maximum power point tracking module, an energy storage device, and any of the above low light detection circuits.

[0014] This invention discloses a low-light detection circuit connected between a photovoltaic module and a maximum power point tracking (MPPT) module. The circuit includes a load module, a relay control module, a sampling module, a feedback control module, and a control signal generation module. The load module, sampling module, and feedback control module are connected in series between the positive and negative terminals of the photovoltaic module. The sampling module samples a voltage representing ambient light. The control signal generation module is electrically connected to the relay control module, sampling module, and feedback control module, and is used to control the relay control module or feedback control module to turn on or off based on the sampled voltage and a reference voltage, thereby controlling the on / off state of the photovoltaic module and the MPPT module based on ambient light. Therefore, this invention achieves low-light detection purely in hardware, without the need for an external MCU, and the circuit is simple, thus enabling low-light detection at low cost and high efficiency. Attached Figure Description

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings: Figure 1 This is a schematic block diagram of a preferred embodiment of the weak light detection circuit of this utility model; Figure 2This is a block diagram of another preferred embodiment of the weak light detection circuit of this utility model; Figure 3 This is a circuit diagram of a preferred embodiment of the weak light detection circuit of this utility model; Figure 4 This is a schematic diagram of a preferred embodiment of the solar power generation system of this utility model. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.

[0017] Figure 1 This is a schematic diagram of a preferred embodiment of the weak light detection circuit 100 of this utility model. Figure 4 This is a schematic block diagram of a preferred embodiment of the solar power generation system of this utility model. Combined with... Figure 1 and 4 It can be seen that the low light detection circuit 100 of this utility model is connected to the photovoltaic module 200 and the maximum power point tracking module. The tracking (MPPT) module 300 includes: a load module 110, a relay control module 120, a sampling module 130, a feedback control module 140, and a control signal generation module 150. The load module 110, the sampling module 130, and the feedback control module 140 are connected in series between the positive terminal PV+ and the negative terminal PV- of the photovoltaic module 200. The relay control module 120 is connected between the positive terminal PV+ of the photovoltaic module 200 and the first terminal of the maximum power point tracking module 300. The negative terminal PV- of the photovoltaic module 200 is connected to the second terminal of the maximum power point tracking module 300. The sampling module 130 is used to sample a sampling voltage representing ambient light. The control signal generation module 150 is electrically connected to the relay control module 120, the sampling module 130, and the feedback control module 140, and is used to control the relay control module 120 or the feedback control module 140 to be turned on or off based on the sampling voltage and a reference voltage.

[0018] In a preferred embodiment of this utility model, the photovoltaic module 200 and the maximum power point tracking module 300 can be constructed using any photovoltaic module and maximum power point tracking module known in the art.

[0019] In a preferred embodiment of the present invention, the load module 110 may include at least one dummy load, such as two dummy loads connected in parallel; the sampling module 130 may include any module, unit or circuit capable of voltage sampling, preferably a sampling resistor, so that the circuit structure can be further simplified.

[0020] The relay control module 120, the feedback control module 140, and the control signal generation module 150 can be constructed using any circuit or module known in the art. For example, the control signal generation module 150 includes a signal amplification unit, a comparator unit, and a latch unit. The signal amplification unit is connected to the sampling module 130 to receive and amplify the sampled voltage. The comparator unit is used to compare the sampled voltage and the reference voltage, and generate a relay control signal and a feedback control signal based on the comparison result. The latch unit is used to latch or output the relay control signal and the feedback control signal. The feedback control module 140 includes a NAND gate and a first switching transistor. The relay control module 120 may include a relay and its corresponding relay drive circuit.

[0021] The low-light detection circuit of this invention is connected between a photovoltaic module and a maximum power point tracking module. The load module, the sampling module, and the feedback control module are connected in series between the positive and negative terminals of the photovoltaic module. The sampling module can sample the voltage representing ambient light. The control signal generation module is electrically connected to the relay control module, the sampling module, and the feedback control module, and is used to control the relay control module or the feedback control module to turn on or off based on the sampled voltage and a reference voltage, thereby controlling the on / off state of the photovoltaic module and the maximum power point tracking module based on ambient light. Therefore, this invention achieves low-light detection purely in hardware, without the need for an external MCU, and the circuit is simple, thus enabling low-light detection at low cost and high efficiency.

[0022] Figure 2 This is a block diagram of another preferred embodiment of the weak light detection circuit of this utility model. (See diagram for example.) Figure 2 As shown, the low light detection circuit 100 of this utility model is connected between the photovoltaic module 200 and the maximum power point tracking module 300, and includes: a load module 110, a relay control module 120, a sampling module 130, a feedback control module 140, a control signal generation module 150, an over-temperature protection module 160, and an auxiliary power source 500.

[0023] The control signal generation module 150 includes a signal amplification unit 151, a comparator unit 152, and a latch unit 153. The signal amplification unit 151 is connected to the sampling module 130 to receive and amplify the sampled voltage; the comparator unit 152 compares the sampled voltage with the reference voltage and generates a relay control signal and a feedback control signal based on the comparison result; the latch unit 153 latches or outputs the relay control signal and the feedback control signal. The over-temperature protection module 160 has its first terminal connected to the load module 110 and its second terminal connected to the signal amplification unit 151 and the comparator unit 152.

[0024] In this preferred embodiment, the power supply voltage required by the weak light detection circuit 100 is obtained through the auxiliary power source 500. For example, an MX8015 power chip is used to convert the input voltage from the photovoltaic module to 5V. This invention uses a control signal generation module 150, composed of a load module 110, a relay control module 120, a sampling module 130, a feedback control module 140, an over-temperature protection module 160, a signal amplification unit 151, a comparator unit 152, and a latch unit 153, to form a pure hardware closed-loop system for real-time monitoring. Its principle is mainly to adjust the weak light threshold by setting the resistance value of the dummy load resistor in the load module, thereby achieving fine adjustment of the light environment conditions for the use of the maximum power point tracking module 300.

[0025] This invention achieves low-light detection purely in hardware, eliminating the need for an external MCU and featuring a simple circuit, thus enabling low-light detection at low cost and high efficiency. Furthermore, in this preferred embodiment, adding an over-temperature protection module can improve the protection level of the solar power generation system.

[0026] Figure 3 This is a circuit diagram of a preferred embodiment of the low-light detection circuit of this utility model. Combined with... Figures 1-3As can be seen, the low-light detection circuit 100 of this utility model is connected between the photovoltaic module 200 and the maximum power point tracking module 300, and includes: a load module 110, a relay control module 120, a sampling module 130, a feedback control module 140, a control signal generation module 150, and an over-temperature protection module 160. The load module 110, the sampling module 130, and the feedback control module 140 are connected in series between the positive terminal PV+ and the negative terminal PV- of the photovoltaic module 200; the relay control module 120 is connected between the positive terminal PV+ of the photovoltaic module 200 and the first terminal of the maximum power point tracking module 300; the negative terminal PV- of the photovoltaic module 200 is connected to the second terminal of the maximum power point tracking module 300. The control signal generation module 150 includes a signal amplification unit 151, a comparator unit 152, and a latch unit 153. The first terminal of the over-temperature protection module 160 is connected to the load module 110, and the second terminal is connected to the signal amplification unit 151 and the comparator unit 152.

[0027] The load module 110 includes two parallel dummy loads R11 and R12; the sampling module 130 includes a sampling resistor RS1. The relay control module 120 includes a switch Q2, resistor R2, resistor R3, diode D2, and relay K. The feedback control module 140 includes a NAND gate U2 and a switch Q1. The signal amplification unit 151 includes an operational amplifier OP1; the comparator unit 152 includes a comparator OP2, diode D1, and resistor R1; the latch unit 153 includes a D latch U1. The over-temperature protection module 160 includes a diode D3, resistor R4, and NTC resistor R5.

[0028] The dummy loads R11 and R12 are connected in parallel between the positive terminal PV+ of the photovoltaic module 200 and the first terminal of the sampling resistor RS1. The inverting input of the operational amplifier OP1 is connected to the first terminal of the sampling resistor RS1, the non-inverting input is connected to the second terminal of the sampling resistor RS1, and the output is connected to the inverting input of the comparator OP2. The non-inverting input of the comparator OP2 is connected to the positive terminal PV+ of the photovoltaic module 200 and the cathode of the diode D1. The anode of the diode D1 is connected to the negative terminal PV- of the photovoltaic module 200 via the resistor R1. The output of the comparator OP2 is connected to the D terminal of the D latch U1. The Q terminal of the D latch U1 is connected to the feedback control module 140 and the relay control module 120, and the LE terminal is connected to the relay control module 120.

[0029] The A terminal of the NAND gate U2 is connected to the first power supply voltage +5V, the B terminal is connected to the Q terminal of the D latch U1, the power supply terminal is connected to the first power supply voltage +5V, the ground terminal GND is connected to the negative terminal PV- of the photovoltaic module 200, and the Y terminal is connected to the control terminal of the switching transistor Q1; the first terminal of the switching transistor Q1 is connected to the negative terminal PV- of the photovoltaic module 200, and the second terminal is connected to the non-inverting input terminal of the operational amplifier OP1 and the second terminal of the sampling resistor RS1.

[0030] The first terminal of the relay K switch is connected to the positive terminal PV+ of the photovoltaic module 200, and the second terminal of the relay K switch is connected to the first terminal of the maximum power point tracking module 300. The first terminal of the coil of the relay K is connected to the cathode of the diode D2, and the second terminal of the coil of the relay K is connected to the LE terminal of the D latch U1. The anode of the diode D2 is connected to the second terminal of the switching transistor Q2, and the control terminal of the switching transistor Q2 is connected to the Q terminal of the D latch U1 via the resistor R2. The first terminal of the switching transistor Q2 is connected to the negative terminal PV- of the photovoltaic module 200. The resistor R3 is connected between the negative terminal PV- of the photovoltaic module 200 and the control terminal of the switching transistor Q2. The first terminal of the NTC resistor R5 is connected to the first power supply voltage +5V, and the second terminal is connected to the anode of the diode D3 via the resistor R4. The cathode of the diode D3 is connected to the output terminal of the operational amplifier OP1 and the inverting input terminal of the comparator OP2.

[0031] In a preferred embodiment of this invention, the switching transistors Q1 and Q2 are NMOS transistors, the control terminal of the switching transistor is the gate of the NMOS transistor, the first terminal of the switching transistor is the drain of the NMOS transistor, and the second terminal of the switching transistor is the source of the NMOS transistor. The NAND gate U2 is an SN74LVC1G00DBVR NAND gate U2; the D latch U1 is an SN74LVC1G373DBVR latch.

[0032] The following will combine Figure 3 The principle of the low-light detection circuit of this utility model is explained as follows. In a solar power generation system, the highest voltage of the photovoltaic module is 80V. Therefore, an auxiliary power source 500 can be used to obtain the first power supply voltage. For example, the MX8015 power supply chip can be used to convert the input voltage of the photovoltaic module to 5V.

[0033] The feedback control module 140 uses an SN74LVC1G00DBVR NAND gate to control whether the load module is connected to the photovoltaic module's circuit. Its working principle is as follows: when the photovoltaic module converts the power supply to 5V through the auxiliary power source 500, it supplies power to the SN74LVC1G00DBVR NAND gate. At the same time, the A terminal of the SN74LVC1G00DBVR NAND gate U2 is connected to a high level, and the B terminal is connected to the Q terminal of the D latch U1. The initial state is a low level, so the output of the SN74LVC1G00DBVR NAND gate is a high level, which controls the switch Q1 to conduct, that is, the system is powered on. The load module 110, the sampling module 120, and the feedback control module 140 are connected in series across the photovoltaic module 200 to form a circuit.

[0034] The sampling module 120 uses sampling resistor RS1, the value of which can be adjusted according to requirements. Since the system's power-on circuit is connected in series across the photovoltaic module, there is voltage on the sampling resistor RS1. Because the voltage is small, it needs to be amplified by operational amplifier OP1 and then compared with the reference voltage set by comparator OP2. D latch U1 uses an SN74LVC1G373DBVRD latch. The LE terminal of D latch U1 is connected to the second terminal of the coil of relay K, with an initial value of 5V high level. The Q terminal of D latch U1 is connected to the control terminal of the switching transistor Q2, and the D terminal of D latch U1 is connected to the output terminal of comparator OP2.

[0035] When the ambient light is weak in the early morning, the voltage sampled by the sampling resistor RS1 is very small. Even after amplification, the signal is lower than the reference voltage of comparator OP2. Therefore, comparator OP2 outputs a low level, the input D terminal of D latch U1 is also low, and the Q terminal follows the state of D terminal as low. Relay K is in the open state, and photovoltaic module 200 cannot be connected to maximum power point tracking module 300. As the ambient light increases, the voltage sampled by the sampling resistor RS1 also increases until it exceeds the reference voltage of comparator OP2. At this time, comparator OP2 outputs a high level, the input D terminal of D latch U1 is also high, and the Q terminal follows the state of D terminal as high. Relay K is in the closed state, and the LE terminal becomes low. The Q terminal no longer follows the change of the input D terminal. This process continues until the ambient light completely cuts off the photovoltaic module input due to time or weather changes, at which point the system resets and repeats. At the same time, the input B terminal of the NAND gate in the feedback control module becomes low because the output Q terminal of the D latch U1 becomes high, thereby cutting off the loop state of the load module, current sampling module and feedback control module.

[0036] Because a dummy load resistor is used for power identification to test whether it is a low-light environment, an additional over-temperature protection module 160 is added to detect the temperature of the load module in case of circuit failure, in order to avoid the risk of overheating caused by the dummy load running for a long time. Its principle is to divide the voltage by NTC resistor R5 and ordinary resistor R4, calculate the voltage represented by the set temperature threshold, and connect it to the input of comparator OP2 through diode D3. When the temperature is too high, the voltage division value will be higher than the set comparison point voltage of comparator OP2, so that the subsequent circuit will work and complete the control of the feedback control module to cut off the loop of load module, current sampling module and feedback control module.

[0037] This invention achieves low-light detection purely in hardware, eliminating the need for an external MCU and featuring a simple circuit, thus enabling low-light detection at low cost and high efficiency. Furthermore, in this preferred embodiment, adding an over-temperature protection module can improve the protection level of the solar power generation system.

[0038] Figure 4 This is a schematic block diagram of a preferred embodiment of the solar power generation system of this utility model. (See diagram for example.) Figure 4 As shown, this utility model also discloses a solar power generation system, including a photovoltaic module 200, a maximum power point tracking module 300, an energy storage device 400, and the aforementioned low light detection circuit 100.

[0039] Here, the photovoltaic module 200, the maximum power point tracking module 300, and the energy storage device 400 are any known photovoltaic modules, maximum power point tracking modules, and energy storage devices; the weak light detection circuit 100 can be constructed based on the foregoing embodiments, and will not be described again here.

[0040] Although this utility model has been described through specific embodiments, those skilled in the art should understand that various modifications and equivalent substitutions can be made to this utility model without departing from its scope. Furthermore, various modifications can be made to this utility model for specific situations or materials without departing from its scope. Therefore, this utility model is not limited to the specific embodiments disclosed, but should include all embodiments falling within the scope of the claims of this utility model.

[0041] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A low-light detection circuit, connected between a photovoltaic module and a maximum power point tracking module, characterized in that, include: Load module, relay control module, sampling module, feedback control module, and control signal generation module; The load module, the sampling module, and the feedback control module are connected in series between the positive and negative terminals of the photovoltaic module; The relay control module is connected between the positive terminal of the photovoltaic module and the first terminal of the maximum power point tracking module; the negative terminal of the photovoltaic module is connected to the second terminal of the maximum power point tracking module. The sampling module is used to sample the voltage representing ambient light. The control signal generation module is electrically connected to the relay control module, the sampling module, and the feedback control module, and is used to control the relay control module or the feedback control module to be turned on or off based on the sampled voltage and the reference voltage.

2. The weak light detection circuit according to claim 1, characterized in that, The control signal generation module includes a signal amplification unit, a comparator unit, and a latch unit; The signal amplification unit is connected to the sampling module to receive and amplify the sampling voltage; The comparator unit is used to compare the sampled voltage and the reference voltage, and generate a relay control signal and a feedback control signal based on the comparison result; The latch unit is used to latch or output the relay control signal and the feedback control signal.

3. The weak light detection circuit according to claim 2, characterized in that, It further includes an over-temperature protection module, the first end of which is connected to the load module, and the second end of which is connected to the signal amplification unit and the comparator unit.

4. The weak light detection circuit according to claim 3, characterized in that, The load module includes two dummy loads connected in parallel; the sampling module includes a sampling resistor.

5. The weak light detection circuit according to claim 4, characterized in that, The signal amplification unit includes an operational amplifier; the comparator unit includes a comparator, a first diode, and a first resistor; the latch unit includes a D latch; The inverting input of the operational amplifier is connected to the first terminal of the sampling resistor, the non-inverting input is connected to the second terminal of the sampling resistor, and the output is connected to the inverting input of the comparator. The non-inverting input of the comparator is connected to the positive terminal of the photovoltaic module and the cathode of the first diode, and the anode of the first diode is connected to the negative terminal of the photovoltaic module through the first resistor. The output of the comparator is connected to the D terminal of the D latch. The Q terminal of the D latch is connected to the feedback control module and the relay control module, and the LE terminal of the D latch is connected to the relay control module.

6. The weak light detection circuit according to claim 5, characterized in that, The feedback control module includes a NAND gate and a first switching transistor; The A terminal of the NAND gate is connected to the first power supply voltage, the B terminal is connected to the Q terminal of the D latch, the power supply terminal is connected to the first power supply voltage, the ground terminal is connected to the negative terminal of the photovoltaic module, and the Y terminal is connected to the control terminal of the first switching transistor. The first terminal of the first switching transistor is connected to the negative terminal of the photovoltaic module, and the second terminal is connected to the non-inverting input terminal of the operational amplifier and the second terminal of the sampling resistor.

7. The weak light detection circuit according to claim 6, characterized in that, The relay control module includes a second switching transistor, a second resistor, a third resistor, a second diode, and a relay; The first terminal of the relay switch is connected to the positive terminal of the photovoltaic module, the second terminal of the relay switch is connected to the first terminal of the maximum power point tracking module, the first terminal of the relay coil is connected to the cathode of the second diode, and the second terminal of the relay coil is connected to the LE terminal of the D latch. The anode of the second diode is connected to the second terminal of the second switching transistor, the control terminal of the second switching transistor is connected to the Q terminal of the D latch via the second resistor, and the first terminal of the second switching transistor is connected to the negative terminal of the photovoltaic module. The third resistor is connected between the negative terminal of the photovoltaic module and the control terminal of the second switching transistor.

8. The weak light detection circuit according to claim 6 or 7, characterized in that, The switching transistor is an NMOS transistor, the control terminal of the switching transistor is the gate of the NMOS transistor, the first terminal of the switching transistor is the drain of the NMOS transistor, and the second terminal of the switching transistor is the source of the NMOS transistor; the NAND gate is an SN74LVC1G00DBVR NAND gate; and the D latch is an SN74LVC1G373DBVR latch.

9. The weak light detection circuit according to claim 5, characterized in that, The over-temperature protection module includes a third diode, a fourth resistor, and an NTC resistor. The first end of the NTC resistor is connected to a first power supply voltage, and the second end is connected to the anode of the third diode via the fourth resistor. The cathode of the third diode is connected to the inverting input of the comparator.

10. A solar power generation system, comprising a photovoltaic module, a maximum power point tracking module, and an energy storage device, characterized in that, It further includes the weak light detection circuit according to any one of claims 1 to 9.

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