Low-voltage direct-current charging and discharging circuit and application thereof in bird repeller

Abstract

The invention relates to a low-voltage direct-current charging and discharging circuit and application of the low-voltage direct-current charging and discharging circuit in a bird repeller, and belongs to the technical field of bird repeller power supply circuits. The low-voltage direct-current charging and discharging circuit comprises a 5V solar panel, a first battery pack, a second battery pack, a first voltage output end, a second voltage output end and a relay; the positive electrode of the second battery pack is controlled to be connected with the first voltage output end / the second voltage output end through a first group of contacts of the relay; the second group of contacts of the relay control the negative electrode of the second battery pack to be connected with the negative electrode of the first battery pack / the first voltage output end, and the first battery pack and the second battery pack are connected in series / in parallel by controlling the actuation and release of the relay so as to provide different output voltages. According to the technical scheme, dynamic battery pack series-parallel connection is achieved through intermittent work, and corresponding working power sources are provided for all working units of the bird repelling device.

Description

Technical Field

[0001] This invention relates to the field of power supply circuit technology for bird repellers, and more particularly to low-voltage DC charging and discharging circuits and their application in bird repellers. Background Technology

[0002] An existing bird deterrent device with a built-in solar panel includes the following operating units: a control system, a starry laser light, a strobe light, an ultrasonic speaker unit, and a voice speaker unit. Among these units, the control system, the starry laser light, and the strobe light operate at 3.5~5V, while the ultrasonic speaker unit and the voice speaker unit operate at 5V or higher. To ensure effective operation of the entire device, two power supplies are required. Common approaches include the following two methods: a. Select a 5~6V solar panel, connect n 18650 lithium batteries in parallel to provide a voltage of 3.7~4.2V, and at the same time provide another 12V voltage through DC-DC converter boost; b. Select a 15V solar panel and connect three 18650 lithium batteries in series to form an 11.1~12.6V battery pack. Use a DC-DC converter to step down the voltage and provide another 3.5~5V voltage.

[0003] Both of the above schemes involve DC-DC conversion, resulting in complex circuits, high output power, low conversion efficiency, and significant energy loss. Scheme b also has the problem of equalizing the charging of series-connected battery packs. Summary of the Invention

[0004] To address the shortcomings and deficiencies of existing technologies, a low-voltage DC charging and discharging circuit and its application in bird deterrents are provided to solve the aforementioned technical problems. By intermittent operation, dynamic series and parallel connection of battery packs is achieved to provide corresponding working power to each working unit of the bird deterrent.

[0005] A low-voltage DC charging and discharging circuit provided to achieve the purpose of this invention includes a solar panel and a relay. Its features include: a first battery pack, a second battery pack, a first voltage output terminal, and a second voltage output terminal. The solar panel is connected to the first battery pack. The positive terminal of the first battery pack is connected to the first voltage output terminal, and the negative terminal of the first battery pack is grounded. The first set of contacts 3, 2, and 4 of the relay controls the connection of the positive terminal of the second battery pack to either the first or second voltage output terminal. The second set of contacts 6, 7, and 5 of the relay controls the connection of the negative terminal of the second battery pack to either the negative terminal of the first battery pack or the first voltage output terminal. When the first set of contacts 3 and 2 of the relay are connected, and the second set of contacts 6 and 7 are connected, the first and second battery packs are connected in parallel. When the first set of contacts 3 and 4 of the relay are connected, and the second set of contacts 6 and 5 are connected, the first and second battery packs are connected in series. By controlling the activation and deactivation of the relay, the first and second battery packs can be connected in parallel or in series to provide different output voltages.

[0006] This technical solution uses two sets of contacts of a two-on, two-off relay to work intermittently to achieve dynamic series and parallel connection of battery packs. By controlling the activation and deactivation of the relay, the first and second battery packs are connected in series / parallel to provide different output voltages to provide corresponding power to each working unit of the bird deterrent device.

[0007] Specifically, when a voltage is output: the control relay connects the positive terminal of the second battery pack to the first voltage output terminal; the negative terminal of the second battery pack is connected to the negative terminal of the first battery pack, realizing the parallel connection of the first battery pack and the second battery pack, and the output voltage is 3.7~4.2V.

[0008] Specifically, when two voltages are output: the control relay connects the positive terminal of the second battery pack to the second voltage output terminal; the negative terminal of the second battery pack is connected to the first voltage output terminal, realizing the series connection of the first battery pack and the second battery pack to provide two output voltages, a first voltage output terminal of 3.7~4.2V and a second voltage output terminal of 7.4~8.4V.

[0009] As a further improvement to the above scheme, both the first battery pack and the second battery pack are composed of several 18650 lithium batteries connected in parallel.

[0010] As a further improvement to the above solution, the solar panel incorporates four 1600mAh 18650 lithium manganese oxide battery cells. The output power of the solar panel is: 5V x 1.6A = 8W.

[0011] As a further improvement to the above solution, the solar panel is a foldable solar panel.

[0012] As a further improvement to the above solution, the solar panel comes with two M10 screws. When the solar panel is unfolded, it is locked in place using the two M10 screws.

[0013] When the low-voltage DC charging and discharging circuit of this technical solution is applied in the scenario of bird deterrence, the entire device is fixed to the tower material of the transmission tower by two U-shaped M10 bolts. The solar panel can rotate 360 ​​degrees horizontally during installation, and the vertical angle of the solar panel is fixed at 45 degrees after installation.

[0014] Because it is a dual-voltage output directly from the battery, it has a large output power and can continuously and stably provide a current output of more than 5A (depending on the battery performance).

[0015] An application of a low-voltage DC charging and discharging circuit in a bird deterrent device further includes a control system and a bird deterrent unit. The bird deterrent unit includes a starry laser light, a strobe light, and an ultrasonic horn. The first output terminal of the low-voltage DC charging and discharging circuit is connected to the starry laser light and the strobe light, and the second output terminal of the low-voltage DC charging and discharging circuit is connected to the ultrasonic horn. The control system is used to control the relay.

[0016] As a further improvement to the above scheme, when the first battery pack and the second battery pack are connected in parallel, the control system of the bird deterrent device, the starry laser light, and the strobe light work, and the working voltage of the starry laser light and the strobe light is 3.7~4.2V.

[0017] As a further improvement to the above solution, when the first battery pack and the second battery pack are connected in series, the bird deterrent's control system, starry laser light, strobe light, ultrasonic speaker unit, and voice speaker unit all operate, providing two output voltages: a first voltage output terminal of 3.7~4.2V and a second voltage output terminal of 7.4~8.4V. The first voltage output terminal is used to power the bird deterrent's control system, starry laser light, and strobe light, while the second voltage output terminal is used to power the ultrasonic speaker unit and the voice speaker unit.

[0018] The beneficial effects of this invention are: Compared with the prior art, the low-voltage DC charging and discharging circuit provided by the present invention, when only the control system of the bird deterrent device, the starry laser light of the bird deterrent unit, and the strobe light are working, uses the two sets of contacts of the first relay and the second relay to connect the first battery pack and the second battery pack in parallel to provide a first voltage output terminal VCC1 of 3.7~4.2V, while charging is performed by a 5V solar panel. At this time, the second voltage output terminal VCC2 has no output. When the bird deterrent unit is working (that is, when the ultrasonic speaker unit and the voice speaker unit also need to work), the first battery pack and the second battery pack are connected in series using the two sets of contacts of the first relay and the second relay to provide two output voltages: the first voltage output terminal VCC1 of 3.7~4.2V and the second voltage output terminal VCC2 of 7.4~8.4V.

[0019] This solution has a simple and reliable structure, no voltage conversion circuit, and low energy loss. Since it is a two-way voltage output directly from the battery, the output power is large and can continuously and stably provide a current output of more than 5A (depending on the battery performance). During charging, all batteries are connected in parallel, the solar charging circuit is simple, and there is no problem of equal charging of the battery pack. Attached Figure Description

[0020] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent upon reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of the invention are illustrated by way of example and not limitation, and like or corresponding reference numerals denote like or corresponding parts, wherein: Figure 1 This is a schematic diagram of the dynamic battery pack series-parallel connection scheme of this technical solution; Figure 2 This provides an equivalent circuit diagram for a single voltage level in this technical solution. Figure 3 The equivalent circuit diagram for this technical solution when there are two voltages is provided.

[0021] Explanation of reference numerals in the attached figures: 10. First battery pack; 20. Second battery pack; 30. Solar panel. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Those skilled in the art should understand that the embodiments described below are only a part of the embodiments disclosed in this technical solution, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] The present invention provides a low-voltage DC charging and discharging circuit, the details of which are as follows: like Figure 1As shown, the device includes a solar panel 30, a relay, a first battery pack 10, a second battery pack 20, a first voltage output terminal VCC1, and a second voltage output terminal VCC2. The solar panel 30 is connected to the first battery pack 10. The positive terminal of the first battery pack 10 is connected to the first voltage output terminal VCC1, and the negative terminal of the first battery pack 10 is grounded. The first set of contacts 3, 2, and 4 of the relay controls the connection of the positive terminal of the second battery pack 20 to either the first voltage output terminal VCC1 or the second voltage output terminal VCC2. The second set of contacts of the relay... Contacts 6, 7, and 5 control the connection between the negative terminal of the second battery pack 20 and the negative terminal of the first battery pack 10 or the first voltage output terminal VCC1. When the first set of contacts 3 of the relay is connected to 2 and the second set of contacts 6 of the relay is connected to 7, the first battery pack 10 and the second battery pack 20 are connected in parallel. When the first set of contacts 3 of the relay is connected to 4 and the second set of contacts 6 of the relay is connected to 5, the first battery pack 10 and the second battery pack 20 are connected in series. By controlling the activation and deactivation of the relay, the first battery pack 10 and the second battery pack 20 can be connected in parallel or in series to provide different output voltages.

[0024] This solution has a simple and reliable structure, no voltage conversion circuit, and low energy loss. Since it is a two-way voltage output directly from the battery, the output power is large and can continuously and stably provide a current output of more than 5A (depending on the battery performance). During charging, all batteries are connected in parallel, the solar charging circuit is simple, and there is no problem of equal charging of the battery pack.

[0025] like Figure 2 As shown, when the horn unit of the bird deterrent unit is not working, and only the control system of the bird deterrent device, the starry laser light of the bird deterrent unit, and the flashing light are working, the relay is controlled to connect the positive terminal of the second battery pack 20 to the first voltage output terminal VCC1; the second set of contacts of the relay controls the negative terminal of the second battery pack 20 to connect to the negative terminal of the first battery pack 10. The first battery pack 10 and the second battery pack 20 are connected in parallel, and the output voltage is 3.7~4.2V. At the same time, the low-voltage DC charging and discharging circuit is charged by the 5V solar panel 30. At this time, there is no output at the second voltage output terminal VCC2. At this point, the specific connection of the equivalent circuit diagram is as follows: The solar panel 30 is connected to the first battery pack 10. The positive terminal of the first battery pack 10 is connected to the first voltage output terminal VCC1, and the negative terminal of the first battery pack 10 is grounded. The positive terminal of the second battery pack 20 is connected to the first voltage output terminal VCC1 through the first set of contacts of the relay; the negative terminal of the second battery pack 20 is connected to the negative terminal of the first battery pack 10 through the second set of contacts of the relay. By controlling the activation and deactivation of the relay, the first battery pack 10 and the second battery pack 20 are connected in parallel to provide an output voltage of 3.7~4.2V.

[0026] This solution features a simple and reliable structure, eliminates the need for voltage conversion circuits, and exhibits low energy loss. When the first battery pack 10 and the second battery pack 20 are connected in parallel, they are in a charging state. Furthermore, the solar charging circuit in this solution is simple and eliminates the issue of equalizing battery pack charging.

[0027] like Figure 3 As shown, when the bird deterrent unit is working (that is, when the ultrasonic speaker unit and the voice speaker unit also need to work), when two voltages are output: the positive terminal of the second battery pack 20 is connected to the second voltage output terminal VCC2 through the first set of contacts of the relay; the negative terminal of the second battery pack 20 is connected to the first voltage output terminal VCC1 through the second set of contacts of the relay. By controlling the activation and deactivation of the relay, the first battery pack 10 and the second battery pack 20 are connected in series to provide two output voltages: the first voltage output terminal VCC1 of 3.7~4.2V and the second voltage output terminal VCC2 of 7.4~8.4V.

[0028] At this point, the specific connection of the equivalent circuit diagram is as follows: The solar panel 30 is connected to the first battery pack 10. The positive terminal of the first battery pack 10 is connected to the first voltage output terminal VCC1, and the negative terminal of the first battery pack 10 is grounded. The positive terminal of the second battery pack 20 is connected to the second voltage output terminal VCC2 through the first set of contacts of the relay; the negative terminal of the second battery pack 20 is connected to the first voltage output terminal VCC1 through the second set of contacts of the relay. By controlling the activation and deactivation of the relay, the first battery pack 10 and the second battery pack 20 are connected in series to provide two output voltages: a first voltage output terminal VCC1 of 3.7~4.2V and a second voltage output terminal VCC2 of 7.4~8.4V.

[0029] This solution has a simple and reliable structure, no voltage conversion circuit, and low energy loss. Since it is a two-way voltage output directly from the battery, the output power is large and can continuously and stably provide a current output of more than 5A (depending on the battery performance).

[0030] In Embodiment 2, both the first battery pack 10 and the second battery pack 20 are composed of several 18650 lithium batteries connected in parallel. These 18650 lithium batteries can be purchased commercially.

[0031] In one embodiment of this technical solution, the solar panel 30 incorporates four 1600mAh 18650 lithium manganese oxide battery cells. These 1600mAh 18650 lithium manganese oxide battery cells can be purchased commercially. The output power of the solar panel 30 is 5V x 1.6A = 8W. The solar panel 30 is configured as a foldable solar panel. The solar panel 30 comes with two M10 screws, which are used to lock the panel in place when it is unfolded.

[0032] When the low-voltage DC charging and discharging circuit of this technical solution is applied in the scenario of bird deterrence, the entire device is fixed to the tower material of the transmission tower by two U-shaped M10 bolts. The solar panel 30 can rotate 360 ​​degrees horizontally during installation, and the vertical angle of the solar panel 30 is fixed at 45 degrees after installation.

[0033] An application of a low-voltage DC charging and discharging circuit in a bird deterrent device further includes a control system and a bird deterrent unit. The bird deterrent unit includes a starry laser light, a strobe light, and an ultrasonic horn. The first output terminal of the low-voltage DC charging and discharging circuit is connected to the starry laser light and the strobe light, and the second output terminal of the low-voltage DC charging and discharging circuit is connected to the ultrasonic horn. The control system is used to control the relay.

[0034] Specifically, when the first battery pack 10 and the second battery pack 20 are connected in parallel, the bird deterrent's control system, the starry laser light, and the strobe light operate. The operating voltage of the starry laser light and the strobe light is 3.7~4.2V, which is powered through the first voltage output terminal VCC1. The specific connection of the equivalent circuit diagram is as follows: Figure 2 As shown; When the first battery pack 10 and the second battery pack 20 are connected in series, the bird deterrent's control system, the starry laser light, the strobe light, the ultrasonic speaker unit, and the voice speaker unit all operate, providing two output voltages: a first voltage output terminal VCC1 of 3.7~4.2V and a second voltage output terminal VCC2 of 7.4~8.4V. The first voltage output terminal VCC1 is used to power the bird deterrent's control system, the starry laser light, and the strobe light, while the second voltage output terminal VCC2 is used to power the ultrasonic speaker unit and the voice speaker unit. The specific connection of the equivalent circuit diagram is as follows. Figure 3 As shown.

[0035] Specifically, the bird deterrent device can use an STM32L010 MCU central controller. The motor driver chip used to drive the ultrasonic speaker unit and the voice speaker unit is set to FM1919.

[0036] In one scenario where the bird repeller is applied according to this technical solution, the specific power consumption of each unit of the bird repeller is shown in the table below:

[0037] According to the data in the table above, two power supplies are required to ensure the effective operation of the bird deterrent device. The common practices are as follows: a. Select a 5~6V solar panel, connect n 18650 lithium batteries in parallel to provide a voltage of 3.7~4.2V, and at the same time provide another 12V voltage through DC-DC converter boost; b. Select a 15V solar panel and connect three 18650 lithium batteries in series to form an 11.1~12.6V battery pack. Use a DC-DC converter to step down the voltage and provide another 3.5~5V voltage.

[0038] Both of the above schemes involve DC-DC conversion, resulting in complex circuits, high output power, low conversion efficiency, and significant energy loss. Scheme b also has the problem of equalizing the charging of series-connected battery packs.

[0039] Considering the intermittent operation of the bird deterrent device, this solution adopts a dynamic series-parallel battery pack scheme, which has a simple structure, no voltage conversion circuit, and low energy loss. Since it is a two-way voltage output directly from the battery, the output power is large and can continuously and stably provide a current output of more than 5A (depending on the battery performance). During charging, all batteries are in parallel, the solar charging circuit is simple, and there is no problem of equal charging of the battery pack.

[0040] When the low-voltage DC charging and discharging circuit of this technical solution is applied in a bird deterrent scenario, the control system, starry laser light, strobe light, ultrasonic speaker unit, and voice speaker unit of the bird deterrent can be configured as follows: The system includes a bird deterrence unit and an auxiliary monitoring unit. Two sets of bird deterrence units can be configured, facing opposite directions, to deter birds on either side of the device. Each bird deterrence unit consists of: a starry laser light, a strobe light, an ultrasonic speaker unit, and a voice speaker unit.

[0041] The starry sky laser light is configured as follows: 40mW flashing 525nm wavelength green starry sky laser light x1; The strobe light settings are: 1 x 3W red visible light strobe light; The ultrasonic speaker unit is configured as follows: 8 x 25kHz fixed-frequency ultrasonic speakers and 4 x 16~30kHz variable-frequency ultrasonic speakers; The speaker unit is set to: 30W speaker x1.

[0042] The auxiliary monitoring unit includes a light sensor, a temperature sensor, and a 4G network communication unit. One light sensor is provided to detect ambient brightness; one temperature sensor is provided to detect device temperature; and one 4G network communication unit is provided to upload the device's operating status.

[0043] When the bird deterrent device is normally in standby mode, and the speaker unit of the bird deterrent unit is not working, only the control system of the bird deterrent device, the starry laser light and the flashing light of the bird deterrent unit need to be working, such as Figure 2As shown, the first battery pack 10 and the second battery pack 20 are connected in parallel using two sets of relay contacts. That is, the positive terminals of the first battery pack 10 and the second battery pack 20 are connected to the first voltage output terminal VCC1, and the negative terminals of the first battery pack 10 and the second battery pack 20 are grounded. At this time, the low-voltage DC charging and discharging circuit provides a 3.7~4.2V first voltage output terminal VCC1. At the same time, the low-voltage DC charging and discharging circuit is charged by the 5V solar panel 30. At this time, the second voltage output terminal VCC2 has no output. At this point, the specific connection of the equivalent circuit diagram is as follows: The solar panel 30 is connected to the first battery pack 10. The positive terminal of the first battery pack 10 is connected to the first voltage output terminal VCC1, and the negative terminal of the first battery pack 10 is grounded. The positive terminal of the second battery pack 20 is connected to the first voltage output terminal VCC1 through the first set of contacts of the relay; the negative terminal of the second battery pack 20 is connected to the negative terminal of the first battery pack 10 through the second set of contacts of the relay. By controlling the activation and deactivation of the relay, the first battery pack 10 and the second battery pack 20 are connected in parallel to provide an output voltage of 3.7~4.2V.

[0044] In standby mode, the bird deterrent unit's speaker unit will activate once every certain period of time (ranging from a few seconds to tens of minutes, dynamically calculated based on the environmental parameters and battery voltage at that time).

[0045] When the bird deterrent unit's speaker unit is working, that is, when both the ultrasonic speaker unit and the voice speaker unit need to work, such as... Figure 3 As shown, the first battery pack 10 and the second battery pack 20 are connected in series using two sets of relay contacts. That is, the negative terminal of the first battery pack 10 is grounded, the positive terminal of the first battery pack 10 is connected to the negative terminal of the second battery pack 20 and connected to the first voltage output terminal VCC1, and the positive terminal of the second battery pack 20 is connected to the second voltage output terminal VCC2, so as to provide two output voltages: the first voltage output terminal VCC1 of 3.7~4.2V and the second voltage output terminal VCC2 of 7.4~8.4V.

[0046] At this point, the specific connection of the equivalent circuit diagram is as follows: The solar panel 30 is connected to the first battery pack 10. The positive terminal of the first battery pack 10 is connected to the first voltage output terminal VCC1, and the negative terminal of the first battery pack 10 is grounded. The positive terminal of the second battery pack 20 is connected to the second voltage output terminal VCC2 through the first set of contacts of the relay; the negative terminal of the second battery pack 20 is connected to the first voltage output terminal VCC1 through the second set of contacts of the relay. By controlling the activation and deactivation of the relay, the first battery pack 10 and the second battery pack 20 are connected in series to provide two output voltages: a first voltage output terminal VCC1 of 3.7~4.2V and a second voltage output terminal VCC2 of 7.4~8.4V.

[0047] When the bird deterrent unit's speaker unit is working, it operates in two modes: ultrasonic bird deterrence and voice bird deterrence. Each time it operates, one mode is randomly selected, accompanied by flashing laser lights and strobe lights. In ultrasonic bird deterrence mode, the ultrasonic frequency alternates between 16kHz and 30kHz, with a duration of approximately 20 seconds. In voice bird deterrence mode, it randomly plays N pre-installed bird deterrent voices, with playback duration determined by the size of each voice file (minimum 15 seconds, otherwise repeating).

[0048] In practical use, the standby interval can be appropriately shortened during the early morning and evening when birds are most active. About two hours after nightfall, the bird deterrent device will enter a deep hibernation state until it starts working again the next morning.

[0049] Regarding ultrasonic and voice bird deterrence, conventional audio decoding and power amplifier chips can be used to drive the voice speaker unit and ultrasonic speaker unit.

[0050] a. Speech source generation: First, several audio files to be played are integrated into a single video file with WAV audio format as the core on a computer according to a custom encoding algorithm. Before the device leaves the factory, this video file is written to a Flash memory chip so that the MCU can read it according to the predetermined format during device operation. When audio playback is required, the MCU reads the relevant data from the memory chip and generates two PCM signals of opposite polarities according to the WAV audio encoding format, providing the audio source for the subsequent power drive.

[0051] b. Generation of ultrasonic sound source: The MCU generates two PCM signals with variable frequency and opposite polarity according to preset frequency parameters and variation rules, providing an ultrasonic sound source for the subsequent power drive. At the same time, it injects tiny signals within the range of human hearing into the PCM according to a certain algorithm, so that the ultrasonic waves can be recognized when they are working (Note: Ultrasonic waves are too high for humans to hear).

[0052] c. Voice and ultrasonic power drive: In this solution, instead of using a conventional audio amplifier chip for analog signal power amplification and output, a dual H-bridge driver chip can be used for power output. The FM1919 is a dual H-bridge driver chip with high output current, commonly used in toy motors, capable of simultaneously controlling the forward and reverse rotation of two sets of motors. This solution can leverage the characteristics of the FM1919 dual H-bridge, using a single chip to simultaneously amplify two PCM signals, one for voice and one for ultrasonic power output.

[0053] The H-bridge is characterized by providing four times the output power of a conventional audio amplifier chip under the same supply voltage. With an 8V supply voltage, its output power is equivalent to that of a conventional audio amplifier chip at 16V.

[0054] Based on the above description in this specification, those skilled in the art will also understand that the following terms used, such as "upper," "lower," "front," "rear," "left," "right," "width," "horizontal," "top," "bottom," "inner," and "outer" (these terms need to be adjusted and replaced according to the specific cases), are terms indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings of this specification. They are only for the purpose of facilitating the explanation of the present invention and simplifying the description, and do not explicitly or implicitly suggest that the device or element involved must have the specific orientation, or be constructed and operated in a specific orientation. Therefore, the above-mentioned orientation or positional relationship terms should not be understood or interpreted as a limitation on the present invention.

[0055] In addition, in the description of this specification, "multiple" means at least two, such as two, three or more, etc., unless otherwise expressly and specifically defined.

Claims

1. A low-voltage DC charging and discharging circuit, comprising a solar panel (30) and a relay, characterized in that: It also includes a first battery pack (10), a second battery pack (20), a first voltage output terminal, and a second voltage output terminal. The solar panel (30) is connected to the first battery pack (10). The positive terminal of the first battery pack (10) is connected to the first voltage output terminal, and the negative terminal of the first battery pack (10) is grounded. The positive terminal of the second battery pack (20) is connected to the first voltage output terminal or the second voltage output terminal through the first set of contacts 3, 2, and 4 of the relay. The second battery pack (20) is controlled by the second set of contacts 6, 7, and 5 of the relay. The negative terminal of the relay is connected to the negative terminal of the first battery pack (10) or the first voltage output terminal. When the first set of contacts 3 of the relay is connected to 2 and the second set of contacts 6 of the relay is connected to 7, the first battery pack (10) and the second battery pack (20) are connected in parallel. When the first set of contacts 3 of the relay is connected to 4 and the second set of contacts 6 of the relay is connected to 5, the first battery pack (10) and the second battery pack (20) are connected in series. By controlling the activation and deactivation of the relay, the first battery pack (10) and the second battery pack (20) are connected in parallel / in series to provide different output voltages.

2. The low-voltage DC charging and discharging circuit according to claim 1, characterized in that: When the control relay is activated, the positive terminal of the second battery pack (20) is connected to the first voltage output terminal; the negative terminal of the second battery pack (20) is connected to the negative terminal of the first battery pack (10), so that the first battery pack (10) and the second battery pack (20) are connected in parallel, and the output voltage is 3.7~4.2V.

3. The low-voltage DC charging and discharging circuit according to claim 1, characterized in that: When the control relay is activated, the positive terminal of the second battery pack (20) is connected to the second voltage output terminal; the negative terminal of the second battery pack (20) is connected to the first voltage output terminal, so that the first battery pack (10) and the second battery pack (20) are connected in series to provide two output voltages, a first voltage output terminal of 3.7~4.2V and a second voltage output terminal of 7.4~8.4V.

4. A low-voltage DC charging and discharging circuit according to any one of claims 1-3, characterized in that: Both the first battery pack (10) and the second battery pack (20) are composed of several 18650 lithium batteries connected in parallel.

5. A low-voltage DC charging and discharging circuit according to any one of claims 1-3, characterized in that: The solar panel (30) has a built-in 4-cell 1600mAh 18650 lithium manganese oxide battery pack.

6. A low-voltage DC charging and discharging circuit according to claim 5, characterized in that: The solar panel (30) is a foldable solar panel.

7. A low-voltage DC charging and discharging circuit according to claim 6, characterized in that: The solar panel (30) comes with two M10 screws.

8. The application of a low-voltage DC charging and discharging circuit according to any one of claims 1-7 in a bird deterrent, characterized in that, It also includes a control system and a bird deterrent unit. The bird deterrent unit includes a starry laser light, a strobe light, and an ultrasonic horn. The first output terminal of the low-voltage DC charging and discharging circuit is connected to the starry laser light and the strobe light. The second output terminal of the low-voltage DC charging and discharging circuit is connected to the ultrasonic horn. The control system is used to control the relay.

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