Photovoltaic charging activation circuit and photovoltaic charging system

Abstract

The embodiment of the utility model discloses a photovoltaic charging activation circuit and a photovoltaic charging system, the photovoltaic charging activation circuit comprises a voltage judgment module, a time delay switch module and a clamping module, the input end of the clamping module is connected with a photovoltaic assembly, and the output end of the clamping module is connected with the input end of the time delay switch module; the clamping module is used for clamping the voltage of the photovoltaic module and outputting an activation signal; the voltage judgment module is connected with the photovoltaic module and is used for outputting a trigger signal when the voltage of the photovoltaic module exceeds a preset threshold value; the controlled end of the time delay switch module is connected with the first output end of the voltage judgment module, and the time delay switch module is used for outputting an activation signal of a preset duration when receiving the trigger signal. According to the embodiment of the utility model, the voltage judgment module accurately controls the time delay switch module, so that stable response can be maintained under the condition that the illumination intensity changes repeatedly, and the adaptability of illumination response is improved; and the time delay switch module can control the duration of the activation signal, so that the reliability of the activation signal is improved.

Description

TECHNICAL FIELD

[0001] The embodiment of the utility model relates to photovoltaic charging field, especially a photovoltaic charging activation circuit and photovoltaic charging system. BACKGROUND

[0002] With the development of solar technology, photovoltaic (PV) charging systems are widely used in power supply of various devices. Photovoltaic panels convert solar energy into electrical energy by absorbing solar energy and charge the battery or other energy storage devices. However, the traditional photovoltaic charging control circuit has some limitations, especially in the response aspect when the sunlight intensity changes.

[0003] The existing photovoltaic charging system usually depends on the output voltage of the photovoltaic panel reaching the threshold value to output an activation signal as the signal to start charging. The traditional activation circuit has the following deficiencies:

[0004] Unable to respond to gradually increasing light conditions: The traditional photovoltaic charging activation circuit can usually only be started when the light rapidly increases. This design may cause the activation signal to be unable to be sent under the condition that the sunlight slowly increases, missing the best charging time.

[0005] The duration of the activation signal is not easy to control: Many traditional activation circuits cannot accurately control the duration of the output signal, which may cause the activation signal to be too long or too short, thereby affecting the start and operation of the rear-end charging module. INVENTION CONTENT

[0006] The technical problem solved by the embodiment of the utility model is to provide a photovoltaic charging activation circuit and photovoltaic charging system, which can solve some problems existing in the existing photovoltaic charging activation circuit.

[0007] To solve the above technical problems, one technical scheme adopted by the utility model is to provide a photovoltaic charging activation circuit, comprising: a voltage judgment module, a delay switch module and a clamping module, the input end of the clamping module is connected with the photovoltaic module, the output end of the clamping module is connected with the input end of the delay switch module, the clamping module is used for clamping the voltage of the photovoltaic module and outputting an activation signal; the voltage judgment module is connected with the photovoltaic module and is used for outputting a trigger signal when the voltage of the photovoltaic module exceeds a preset threshold value; the controlled end of the delay switch module is connected with the first output end of the voltage judgment module, and is used for outputting the activation signal with a preset duration when receiving the trigger signal.

[0008] In some embodiments, the circuit further comprises a capacitor discharge module connected with the delay switch module, and a controlled end of the capacitor discharge module is connected with a second output end of the voltage judgment module; the capacitor discharge module is configured to discharge the delay switch module when the voltage of the photovoltaic module is lower than the preset threshold.

[0009] In some embodiments, the voltage judgment module comprises a voltage dividing unit and a comparison unit; the voltage dividing unit is connected with the photovoltaic module and configured to divide the voltage of the photovoltaic module by a preset ratio; an input end of the comparison unit is connected with an output end of the voltage dividing unit, and configured to compare the divided voltage with a preset reference voltage, and output the trigger signal when the divided voltage is greater than the reference voltage.

[0010] In some embodiments, the voltage dividing unit comprises a resistor R4 and a resistor R5, the comparison unit comprises a reference source U1 and a second reference source U2, a first end of the resistor R4 is connected with a positive electrode of the photovoltaic module, a second end of the resistor R4, a first end of the resistor R5, a controlled end of the reference source U1 and a controlled end of the reference source U2 are connected, a cathode of the reference source U1 is connected with a controlled end of the delay switch module, a cathode of the reference source U2 is connected with a controlled end of the capacitor discharge module, an anode of the reference source U1, an anode of the reference source U2 and a second end of the resistor R5 are connected with a negative electrode of the photovoltaic module.

[0011] In some embodiments, the delay switch module comprises a delay unit and a switch unit; an input end of the delay unit is connected with an output end of the voltage judgment module, and configured to generate a delay signal according to the trigger signal; a controlled end of the switch unit is connected with an output end of the delay unit, and an input end of the switch unit is connected with an output end of the clamping module, and configured to control the output of the activation signal according to the delay signal.

[0012] In some embodiments, the delay unit comprises a resistor R1 and a capacitor C1, the switch unit comprises a switch tube Q3, a first end of the resistor R1, an output end of the clamping module and a source of the switch tube Q3 are connected, a second end of the resistor R1, a gate of the switch tube Q3 and a first end of the capacitor C1 are connected, a second end of the capacitor C1 is connected with a first output end of the voltage judgment module, and a drain of the switch tube Q3 is connected with a subsequent circuit.

[0013] In some embodiments, the capacitor discharging module comprises a discharging control unit and a discharging path unit; the discharging control unit is connected with the second output end of the voltage judging module, and is used for turning on the discharging path unit when the voltage of the photovoltaic module is lower than the preset threshold; the discharging path unit is connected with the delay switch module, and is used for providing a discharging path for the delay switch module when turned on.

[0014] In some embodiments, the discharging control unit comprises a resistor R2, the discharging path unit comprises a resistor R3 and a transistor Q1, the first end of the resistor R2 is connected with the output end of the clamping module, the second end of the resistor R2 is connected with the base of the transistor Q1 and the second output end of the voltage detecting module, the emitter of the transistor Q1 is connected with the first end of the resistor R3, the second end of the resistor R3 is connected with the second end of a capacitor C1, and the collector of the transistor Q1 is connected with the first end of the capacitor C1.

[0015] In some embodiments, the clamping module comprises a transistor Q2, a resistor R6 and a voltage stabilizing diode D4, the collector of the transistor Q2 is connected with the positive pole of the photovoltaic module and the first end of the resistor R6, the base of the transistor Q2 is connected with the second end of the resistor R6 and the cathode of the voltage stabilizing diode D4, the emitter of the transistor Q2 is connected with the input end of the delay switch module, and the anode of the voltage stabilizing diode D4 is connected with the negative pole of the photovoltaic module.

[0016] To solve the above technical problems, the utility model adopts another technical scheme, which provides a photovoltaic charging system, characterized by comprising: a photovoltaic module; and a photovoltaic charging activation circuit as described above.

[0017] The utility model embodiment has the advantages that, unlike the prior art, the utility model embodiment can maintain stable response under repeated changes of light intensity through precise control of the delay switch module by the voltage judging module, thereby improving the adaptability of light response; the delay switch module can control the duration of the activation signal, thereby improving the reliability of the activation signal; in addition, the clamping module clamps the high voltage of the photovoltaic module to a safe range, thereby effectively protecting the subsequent circuit and improving the reliability and stability of the activation circuit. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a structural schematic view of a photovoltaic charging activation circuit provided by the utility model embodiment;

[0019] Figure 2 is a structural schematic view of another photovoltaic charging activation circuit provided by the utility model embodiment;

[0020] Figure 3 is a structure schematic diagram of a voltage comparison module provided by the embodiment of the utility model;

[0021] Figure 4 is a structure schematic diagram of a delay switch module provided by the embodiment of the utility model;

[0022] Figure 5 is a structure schematic diagram of a capacitor discharge module provided by the embodiment of the utility model;

[0023] Figure 6 is a circuit principle diagram of a photovoltaic charging activation circuit provided by the embodiment of the utility model. DETAILED DESCRIPTION

[0024] In order to facilitate understanding of the utility model, the utility model is explained in more detail below in combination with the drawings and specific embodiments. It should be noted that when an element is described as "fixed to" another element, it can be directly on the other element or one or more intervening elements can be present therebetween. When an element is described as "connected to" another element, it can be directly connected to the other element or one or more intervening elements can be present therebetween. The terms "vertical", "horizontal", "left", "right" and similar expressions used in the specification are only for the purpose of illustration.

[0025] Unless otherwise defined, all technical and scientific terms used in the specification are the same as the meanings commonly understood by those skilled in the art to which the utility model belongs. The terms used in the specification of the utility model are only for the purpose of describing the specific embodiments and are not used to limit the utility model. The term "and / or" used in the specification includes any and all combinations of one or more related listed items.

[0026] As Figure 1 shown, the embodiment provides a photovoltaic charging activation circuit 10, including voltage judgment module 120, delay switch module 130 and clamping module 110. Wherein, the input end of clamping module 110 is connected with photovoltaic module 20, and the output end of clamping module 110 is connected with the input end of delay switch module 130. The input end of voltage judgment module 120 is connected with photovoltaic module 20, and the controlled end of delay switch module 130 is connected with the first output end of voltage judgment module 120, and the output end of delay switch module 130 and post-stage circuit 30 are connected. As an example but not limited, post-stage circuit 30 can be a charging management unit, a controller and other circuits for receiving activation signals.

[0027] In this embodiment, the clamping module 110 is used to clamp the high voltage output by the photovoltaic assembly 20 (also referred to as a PV panel or a solar panel) within a safe range (for example, 3.3V-5V), ensuring that the voltage amplitude of the output activation signal is suitable for use by the subsequent circuit 30. The voltage judgment module 120 is used to monitor the output voltage of the photovoltaic assembly 20 in real time, and outputs a trigger signal to the delay switch module 130 when it is detected that the voltage exceeds a preset threshold (for example, 8V). The delay switch module 130 outputs an activation signal of a preset duration (for example, 100ms) to the subsequent circuit 30 after receiving the trigger signal.

[0028] The photovoltaic charging activation circuit 10 of this embodiment realizes effective monitoring and control of the output voltage of the photovoltaic assembly 20 through the cooperation of the three functional modules. When the intensity of sunlight changes, causing the output voltage of the photovoltaic assembly 20 to change, the circuit can respond in time and output a suitable activation signal, solving the problem of the slow response of the traditional circuit when the light changes slowly.

[0029] As shown in FIG. 1, Figure 2 The photovoltaic charging activation circuit 10 of this embodiment further includes a capacitor discharge module 140 on the basis of the first embodiment. The capacitor discharge module 140 is electrically connected to the delay switch module 130, and the controlled end of the capacitor discharge module 140 is connected to the second output end of the voltage judgment module 120.

[0030] Specifically, when the output voltage of the photovoltaic assembly 20 is lower than the preset threshold (for example, the output voltage drops to 6V due to weakening of the light), the voltage judgment module 120 controls the capacitor discharge module 140 to discharge the energy storage element (such as a capacitor) in the delay switch module 130 through the second output end. The purpose of this design is to ensure that the delay switch module 130 can reset quickly in the case of repeated and rapid changes in the intensity of the light, so as to prepare for the next output of the activation signal.

[0031] By way of example but not limitation, the delay switch module 130 can include an RC delay circuit, and the capacitor discharge module 140 adjusts the charging and discharging state of the capacitor in the RC circuit by controlling whether the discharge path is turned on or not. When the light weakens, the capacitor is discharged in time to avoid the influence of the residual voltage of the capacitor on the timing of the next trigger, thereby improving the response capability of the circuit when the light frequently changes.

[0032] This embodiment further improves the function of the photovoltaic charging activation circuit by adding the capacitor discharge module 140, so that it can not only respond to the increase in light, but also reset quickly when the light weakens, thereby improving the adaptability and reliability of the circuit.

[0033] As shown in FIG. 2, Figure 3As shown, the embodiment mainly shows the specific structure of the voltage judgment module 120, which includes a voltage dividing unit 121 and a comparison unit 122. The input end of the voltage dividing unit 121 is connected with the photovoltaic module 20, for dividing the output voltage of the photovoltaic module 20 according to a preset ratio. The input end of the comparison unit 122 is connected with the output end of the voltage dividing unit 121, for comparing the divided voltage with a preset reference voltage (for example, 2.5V).

[0034] As an example but not limitation, the voltage dividing unit 121 can adopt a resistance voltage dividing network, and the dividing ratio can be set by reasonably selecting the resistance value. The comparison unit 122 can adopt a precision adjustable reference source (such as TL431), which has the characteristics of small temperature coefficient and good stability. When the divided voltage exceeds the reference voltage, the comparison unit 122 outputs a trigger signal to the delay switch module 130, and controls the capacitor discharging module 140 through another output at the same time.

[0035] The structure design of voltage dividing and comparison not only realizes the accurate detection of the photovoltaic voltage, but also can flexibly set the trigger threshold by adjusting the dividing ratio, thereby improving the versatility and adjustability of the circuit.

[0036] As shown, the embodiment mainly shows the specific structure of the voltage judgment module 120, which includes a voltage dividing unit 121 and a comparison unit 122. The input end of the voltage dividing unit 121 is connected with the photovoltaic module 20, for dividing the output voltage of the photovoltaic module 20 according to a preset ratio. The input end of the comparison unit 122 is connected with the output end of the voltage dividing unit 121, for comparing the divided voltage with a preset reference voltage (for example, 2.5V). Figure 4 As shown, the embodiment mainly shows the internal structure of the delay switch module 130, which includes a delay unit 131 and a switch unit 132. The input end of the delay unit 131 is connected with the output end of the voltage judgment module 120, the output end of the delay unit 131 and the controlled end of the switch unit 132 are connected, the input end of the switch unit 132 is connected with the output end of the clamping module 110, and the delay unit 131 is also connected with the capacitor discharging module 140.

[0037] As an example but not limitation, the delay unit 131 can adopt an RC time constant circuit, for converting the trigger signal output by the voltage judgment module 120 into a delay signal with a specific duration. The switch unit 132 can use a switch tube, whose gate is controlled by the delay signal, and the source-drain is used for turning on or turning off the output path of the activation signal.

[0038] After the voltage judgment module 120 outputs the trigger signal, the capacitor of the delay unit 131 starts to charge, and in the charging process, the switch unit 132 is turned on, so that the clamped voltage signal can be transmitted to the subsequent circuit 30. By adjusting the RC time constant, the pulse width of the activation signal can be accurately controlled, thereby avoiding the problem that the duration of the activation signal is not easy to control in the traditional photovoltaic charging activation circuit.

[0039] As shown, the embodiment mainly shows the specific structure of the voltage judgment module 120, which includes a voltage dividing unit 121 and a comparison unit 122. The input end of the voltage dividing unit 121 is connected with the photovoltaic module 20, for dividing the output voltage of the photovoltaic module 20 according to a preset ratio. The input end of the comparison unit 122 is connected with the output end of the voltage dividing unit 121, for comparing the divided voltage with a preset reference voltage (for example, 2.5V). Figure 5As shown, the embodiment describes a specific implementation of the capacitor discharge module 140, which is composed of a discharge control unit 141 and a discharge path unit 142. The discharge control unit 141 is connected to the second output of the voltage judgment module 120, and the discharge path unit 142 is connected to the delay switch module 130.

[0040] As an example but not limitation, the discharge control unit 141 can be composed of a bias resistor for controlling the conduction state of the discharge path. The discharge path unit 142 can be composed of a switch tube to provide a discharge path for the energy storage element in the delay switch module 130.

[0041] In operation, when the voltage of the photovoltaic module is lower than the threshold value, the second output of the voltage judgment module 120 changes in level, and the discharge path unit 142 is turned on through the discharge control unit 141. At this time, the capacitor in the delay switch module 130 can quickly release the charge through the discharge path, ensuring that the circuit can quickly respond to the next light change.

[0042] The design of the double-unit structure not only ensures the controllability of the discharge process, but also improves the efficiency of capacitor discharge through appropriate discharge path configuration, so that the circuit can still work reliably in the scene of frequent changes in light.

[0043] In some embodiments of the present application, a circuit schematic diagram of a photovoltaic charging activation circuit is provided, as shown in Figure 6 The voltage division unit includes resistors R4 and R5, the comparison unit includes reference source U1 and second reference source U2, the delay unit includes resistor R1 and capacitor C1, the switch unit includes switch tube Q3, the discharge control unit includes resistor R2, the discharge path unit includes resistor R3 and transistor Q1, and the clamping module includes transistor Q2, resistor R6 and zener diode D4.

[0044] The first end of resistor R4 is connected to the positive electrode of the photovoltaic module PV, and the second end of resistor R4 is connected to the first end of resistor R5, the controlled end of reference source U1 and the controlled end of reference source U2. The anode of reference source U1, the anode of reference source U2 and the second end of resistor R5 are connected to the negative electrode of the photovoltaic module PV.

[0045] The collector of transistor Q2 is connected to the positive electrode of the photovoltaic module PV and the first end of resistor R6, the base of transistor Q2 is connected to the second end of resistor R6 and the cathode of zener diode D4, and the anode of zener diode D4 is connected to the negative electrode of the photovoltaic module PV.

[0046] The first end of the resistor R1 is connected with the emitter of the triode Q2 and the source of the switch tube Q3, the second end of the resistor R1 is connected with the gate of the switch tube Q3 and the first end of the capacitor C1, the second end of the capacitor C1 is connected with the cathode of the reference source U1, and the drain of the switch tube Q3 is connected with the output circuit.

[0047] The first end of the resistor R2 is connected with the emitter of the triode Q2, the second end of the resistor R2 is connected with the base of the triode Q1 and the cathode of the reference source U2, the emitter of the triode Q1 is connected with the first end of the resistor R3, the second end of the resistor R3 is connected with the second end of the capacitor C1, and the collector of the triode Q1 is connected with the first end of the capacitor C1.

[0048] The clamping module 110 adopts a "triode-zener diode" (triode Q2 and zener diode D4) structure, and bias is provided through the resistor R6. The collector of the triode Q2 receives the photovoltaic input, the emitter of the triode Q2 outputs the clamped signal, and the base of the triode Q2 is connected with the zener diode D4 through the resistor R6 to form a clamping circuit. The "triode-zener diode" structure can clamp the photovoltaic voltage of any amplitude to Uz-Vbe (Uz is the voltage stabilization value of the zener diode D4, and Vbe is the conduction voltage drop of the triode Q2), thereby providing a stable and reliable working voltage for the subsequent circuit.

[0049] The voltage judgment module 120 adopts a double-reference source (reference source U1 and reference source U2) structure, and cooperates with the voltage dividing resistors R4 and R5 to realize voltage detection. The voltage dividing point of the resistor R4 and the resistor R5 is connected with the control ends of the reference source U1 and the reference source U2 at the same time, when the voltage dividing voltage exceeds the reference voltage (2.5V) of the reference source, the two reference sources are turned on at the same time, and control the delay switch module 130 and the capacitor discharge module 140 respectively. The design of the double-reference source improves the reliability of voltage detection.

[0050] The delay switch module 130 realizes timing control through the combination of the RC delay circuit (resistor R1 and capacitor C1) and the field effect tube switch tube Q3. When the reference source U1 is turned on, the capacitor C1 is charged through the resistor R1, and in the charging process, the gate potential of the switch tube Q3 is lowered to cause it to be turned on, thereby outputting a narrow pulse signal determined by the RC time constant. The combination of the RC delay circuit and the field effect tube ensures that the activation signal has a stable time width.

[0051] The capacitor discharge module 140 includes discharge control (resistor R2) and discharge path (triode Q1 and resistor R3). When the light weakens to cause the reference source U2 to be turned off, the triode Q1 is turned on under the bias of the resistor R2 to provide a fast discharge path for the capacitor C1. The discharge design of the discharge control and the discharge path significantly improves the response speed of the circuit when the light frequently changes.

[0052] Working process: when the light intensity increases and the partial pressure voltage exceeds the preset threshold (such as 2.5V), the reference source U1 and the reference source U2 are turned on at the same time, on the one hand, the RC delay and the switch tube Q3 output the activation signal, on the other hand, the triode Q1 is cut off to avoid interference signal output; when the light intensity decreases, the reference source U1 and the reference source U2 are turned off, the triode Q1 is turned on to quickly discharge the capacitor C1, and preparation is made for the next trigger. The whole process is automatically completed without external control.

[0053] Through the above mode, the utility model discloses the accurate control of the delay switch module through the voltage judgment module, can keep stable response under the condition that the illumination intensity repeatedly changes, improves the adaptability of illumination response, and the delay switch module can control the duration of activation signal, improves the reliability of activation signal, in addition, the clamping module clamps the high voltage of photovoltaic module to the safety range, effectively protects the later stage circuit, improves the reliability and stability of activation circuit.

[0054] Based on any one of the photovoltaic charging activation circuits provided in the above embodiments, the utility model further provides a photovoltaic charging system, which comprises a photovoltaic module and the photovoltaic charging activation circuit according to any one of the above embodiments.

[0055] It should be noted that the specification and drawings of the utility model give the preferred embodiments of the utility model, but the utility model can be realized in many different forms, and is not limited to the embodiments described in the specification, and the embodiments are not as additional limitation on the content of the utility model, and the purpose of providing these embodiments is to make the understanding of the disclosure of the utility model more thorough and comprehensive. Furthermore, the above technical features continue to combine, form various embodiments not listed above, and are regarded as the range of the specification of the utility model; further, for those skilled in the art, the above description can be improved or changed, and all these improvements and changes should belong to the protection scope of the claims of the utility model.

Claims

1. A photovoltaic charge activation circuit, characterized by, The application relates to a photovoltaic module voltage protection device. The device comprises a voltage judging module, a delay switch module and a clamping module. The input end of the clamping module is connected with a photovoltaic module, the output end of the clamping module is connected with the input end of the delay switch module, and the clamping module is used for clamping the voltage of the photovoltaic module and outputting an activation signal. The voltage judging module is connected with the photovoltaic module and is used for outputting a trigger signal when the voltage of the photovoltaic module exceeds a preset threshold value. The controlled end of the delay switch module is connected with the first output end of the voltage judging module, and the delay switch module is used for outputting the activation signal with a preset time length when the trigger signal is received.

2. The circuit of claim 1, wherein, The device further comprises a capacitor discharging module. The capacitor discharging module is connected with the delay switch module, and the controlled end of the capacitor discharging module is connected with the second output end of the voltage judging module. The capacitor discharging module is used for discharging the delay switch module when the voltage of the photovoltaic module is lower than the preset threshold value.

3. The circuit of claim 2, wherein, The voltage judging module comprises a voltage dividing unit and a comparison unit. The voltage dividing unit is connected with the photovoltaic module and is used for dividing the voltage of the photovoltaic module by a preset ratio. The input end of the comparison unit is connected with the output end of the voltage dividing unit, the comparison unit is used for comparing the divided voltage with a preset reference voltage, and the trigger signal is outputted when the divided voltage is greater than the reference voltage.

4. The circuit of claim 3, wherein, The voltage dividing unit comprises a resistor R4 and a resistor R5, the comparison unit comprises a reference source U1 and a second reference source U2, the first end of the resistor R4 is connected with the positive electrode of the photovoltaic module, the second end of the resistor R4, the first end of the resistor R5, the controlled end of the reference source U1 and the controlled end of the second reference source U2 are connected, the cathode of the reference source U1 is connected with the controlled end of the delay switch module, the cathode of the second reference source U2 is connected with the controlled end of the capacitor discharging module, and the anode of the reference source U1, the anode of the second reference source U2 and the second end of the resistor R5 are connected with the negative electrode of the photovoltaic module.

5. The circuit of claim 1, wherein, The delay switch module comprises a delay unit and a switch unit. The input end of the delay unit is connected with the output end of the voltage judging module, and the delay unit is used for generating a delay signal according to the trigger signal. The controlled end of the switch unit is connected with the output end of the delay unit, the input end of the switch unit is connected with the output end of the clamping module, and the switch unit is used for controlling the output of the activation signal according to the delay signal.

6. The circuit of claim 5, wherein, The delay unit comprises a resistor R1 and a capacitor C1, and the switch unit comprises a switch tube Q3. The first end of the resistor R1, the output end of the clamping module and the source electrode of the switch tube Q3 are connected, the second end of the resistor R1, the gate electrode of the switch tube Q3 and the first end of the capacitor C1 are connected, the second end of the capacitor C1 is connected with the first output end of the voltage judging module, and the drain electrode of the switch tube Q3 is connected with a subsequent circuit.

7. The circuit of claim 2, wherein, The capacitor discharging module comprises a discharging control unit and a discharging path unit. The discharge control unit is connected with the second output end of the voltage judging module, and is used for turning on the discharge path unit when the voltage of the photovoltaic module is lower than the preset threshold value; The discharge path unit is connected with the delay switch module, and is used for providing a discharge path for the delay switch module when being turned on.

8. The circuit of claim 7, wherein, The discharge control unit comprises a resistor R2, and the discharge path unit comprises a resistor R3 and a triode Q1, The first end of the resistor R2 is connected with the output end of the clamping module, the second end of the resistor R2 is connected with the base of the triode Q1 and the second output end of the voltage detecting module, the emitter of the triode Q1 is connected with the first end of the resistor R3, the second end of the resistor R3 is connected with the second end of a capacitor C1, and the collector of the triode Q1 is connected with the first end of the capacitor C1.

9. The circuit according to any of claims 1-8, characterized in that, The clamping module comprises a triode Q2, a resistor R6 and a stabilizing diode D4, The collector of the triode Q2 is connected with the positive pole of the photovoltaic module and the first end of the resistor R6, the base of the triode Q2 is connected with the second end of the resistor R6 and the cathode of the stabilizing diode D4, the emitter of the triode Q2 is connected with the input end of the delay switch module, and the anode of the stabilizing diode D4 is connected with the negative pole of the photovoltaic module.

10. A photovoltaic charging system, characterized by, It comprises: a photovoltaic module; a photovoltaic charging activation circuit according to any one of claims 1-9.

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