Load detection circuit

Abstract

The utility model discloses a load detection circuit which is used for detecting the connection state of a load in a charging and discharging circuit. The load detection circuit includes a switching element, a first resistor, and a controller. The input end of the switch element is connected with the power supply, and the output end is connected with the controller. The input end of the first resistor is connected with the first output end of the switch element, and the output end of the first resistor is connected with the common end of the DC-DC converter switch pin and the energy storage element in the charging and discharging circuit. The direct current-direct current converter comprises a pulse frequency modulation working mode, in the pulse frequency modulation working mode, the common end transmits a low level signal to the first output end of the switch element through the first resistor, so that the switch element is in a conducting state, and the second output end of the switch element transmits a first electric signal output by the power supply end to the controller; when the first electric signal is smaller than a preset value, the controller sends a load disconnection instruction to the charging and discharging circuit or a load in the charging and discharging circuit is in a disconnection state.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, specifically to a load detection circuit. This application also relates to a charging and discharging circuit, a mobile charging and discharging device, a solar charging and discharging device, and an off-grid solar energy system. Background Technology

[0002] The load detection function is primarily used in power banks with high protection requirements. Once the power bank has finished charging the phone, its charging function should be turned off. This saves power consumption and disconnects power to the charging port, ensuring its durability. If the charging port is not disconnected in time, it will undergo electrochemical reactions and corrode under high humidity or rainy conditions.

[0003] Existing technologies typically use sampling resistors and amplification circuits to detect whether a load is disconnected. A sampling resistor is connected in series with the load circuit. The current flowing through the load creates a voltage drop across the sampling resistor. This voltage drop is amplified by the sampling amplifier circuit and then fed into a microcontroller for ADC sampling, allowing the microcontroller to determine the current load current. When the load is disconnected, the current approaches zero, thus indicating that the load has been disconnected. This technique requires adding a sampling resistor to the load's discharge circuit, which consumes energy and reduces circuit efficiency. Furthermore, it necessitates the addition of a sampling amplifier circuit, resulting in higher implementation costs. Utility Model Content

[0004] This application provides a load detection circuit to address the problems of low loop efficiency, high power consumption, and high implementation cost of existing load detection circuits. This application also provides a charging / discharging circuit, a mobile charging / discharging device, a solar charging / discharging device, and an off-grid solar system.

[0005] This application provides a load detection circuit for detecting the connection status of a load in a charging and discharging circuit. The load detection circuit includes a switching element, a first resistor, and a controller. The input terminal of the switching element is connected to a power supply, and the output terminal of the switching element is connected to the controller. The input terminal of the first resistor is connected to the first output terminal of the switching element, and the output terminal of the first resistor is connected to the common terminal of the DC-DC converter switch pin and the energy storage element in the charging and discharging circuit. The DC-DC converter includes a pulse frequency modulation operating mode. In the pulse frequency modulation operating mode, the common terminal transmits a low-level signal to the first output terminal of the switching element through the first resistor, causing the switching element to be in a conducting state. The second output terminal of the switching element transmits the first electrical signal output from the power supply to the controller. When the first electrical signal is less than a preset value, the controller sends a load disconnect command to the charging and discharging circuit or the load in the charging and discharging circuit is in a disconnected state.

[0006] Optionally, a filtering circuit is also included. The filtering circuit includes a filtering resistor and a filtering capacitor. The input terminal of the filtering resistor is connected to the second output terminal of the switching element, the output terminal of the filtering resistor is connected to the controller, the input terminal of the filtering capacitor is connected between the filtering resistor and the controller, and the output terminal of the filtering capacitor is grounded.

[0007] Optionally, the preset value is the value of the second electrical signal when the load is at a preset capacity.

[0008] Optionally, the DC-DC converter includes: buck conversion type and boost conversion type; when the DC-DC converter is a buck conversion type, the output terminal of the first resistor is connected to the common terminal between the input terminal of the energy storage element and the switch pin; when the DC-DC converter is a boost conversion type, the output terminal of the first resistor is connected to the common terminal between the output terminal of the energy storage element and the switch pin.

[0009] Optionally, a first capacitor may also be included, which is connected in parallel with a first resistor.

[0010] Optionally, a second resistor is also included, with its input terminal connected to a power supply and its output terminal connected to the input terminal of a switching element.

[0011] This application also provides a charging and discharging circuit, including: a charging and discharging circuit and a load detection circuit, wherein the load detection circuit is the load detection circuit described above.

[0012] This application also provides a mobile charging and discharging device, including: a housing, and a plurality of connection ports disposed on the housing; the plurality of connection ports are respectively used to connect to a device to be charged, and to connect the mobile charging device to a power supply when the mobile charging device needs to be charged; a charging and discharging circuit is disposed inside the housing, and the charging and discharging circuit includes the aforementioned load detection circuit.

[0013] This application also provides a solar charging and discharging device, including: a solar panel, and a charging and discharging device connected to the solar panel, the charging and discharging device including a charging and discharging circuit, and the aforementioned load detection circuit.

[0014] This application also provides an off-grid solar energy system, including: a solar panel, a charging and discharging device, and an electronic device; the solar panel is connected to the charging and discharging device for converting the energy of the solar panel into electrical energy to charge the charging and discharging device, the charging and discharging device is used to store electrical energy and charge the electronic device when connected, and the charging and discharging device includes a charging and discharging circuit and the aforementioned load detection circuit.

[0015] Compared with the prior art, this application has the following advantages:

[0016] This application employs a DC-DC converter with a pulse frequency adjustment operating mode. It utilizes a load detection circuit to detect the connection status of the load in the charging / discharging circuit. When the first electrical signal is less than a preset value, a load disconnection command is sent to the charging / discharging circuit, or the load in the charging / discharging circuit is in a disconnected state, thus realizing the load detection function. This application eliminates the sampling resistor and sampling amplification circuit found in existing technologies, reducing the implementation cost of the load detection function. Simultaneously, it also reduces the output internal resistance in the charging / discharging circuit, decreasing energy consumption and improving loop efficiency. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the load detection circuit in the prior art;

[0018] Figure 2 This is a schematic diagram of the load detection circuit based on the DC-DC BUCK circuit provided in this application;

[0019] Figure 3 This is a schematic diagram of the load detection circuit based on the DC-DC BOOST circuit provided in this application;

[0020] Figure 4 This is a schematic diagram of the first embodiment of the load detection circuit based on the DC-DC BUCK circuit provided in this application;

[0021] Figure 5 This is a schematic diagram of the second embodiment of the load detection circuit based on the DC-DC BOOST circuit provided in this application. Detailed Implementation

[0022] Many specific details are set forth in the following description to provide a full understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of this application; therefore, this application is not limited to the specific embodiments disclosed below.

[0023] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit the application. The descriptive terms used in this application and the appended claims, such as "a," "first," and "second," are not intended to limit quantity or sequence, but rather to distinguish information of the same type from one another.

[0024] Existing technologies typically employ sampling resistors and amplification circuits to detect whether the load is disconnected. For example... Figure 1As shown, a sampling resistor is connected in series in the circuit containing the load. The current flowing through the load generates a voltage drop across the sampling resistor. This voltage drop is amplified by a sampling amplifier circuit and then fed into the microcontroller for ADC sampling, allowing the microcontroller to determine the current load current. When the load is disconnected, the current approaches zero, indicating that the load has been disconnected. This technique requires adding a sampling resistor to the load's discharge circuit, which consumes energy and reduces circuit efficiency. Furthermore, existing techniques necessitate the addition of a sampling amplifier circuit, increasing implementation costs.

[0025] This application provides a load detection circuit to solve the problems of low loop efficiency, high power consumption and high implementation cost of existing load detection circuits.

[0026] This application provides a load detection circuit for detecting the connection status of a load in a charging and discharging circuit. The load detection circuit includes a switching element, a first resistor, and a controller. The input terminal of the switching element is connected to a power supply, and the output terminal of the switching element is connected to the controller. The input terminal of the first resistor is connected to the first output terminal of the switching element, and the output terminal of the first resistor is connected to the common terminal of the DC-DC converter switch pin and the energy storage element in the charging and discharging circuit. The DC-DC converter includes a pulse frequency modulation operating mode. In the pulse frequency modulation operating mode, the common terminal transmits a low-level signal to the first output terminal of the switching element through the first resistor, causing the switching element to be in a conducting state. The second output terminal of the switching element transmits the first electrical signal output from the power supply to the controller. When the first electrical signal is less than a preset value, the controller sends a load disconnect command to the charging and discharging circuit or the load in the charging and discharging circuit is in a disconnected state.

[0027] The load detection circuit provided in this application can be used to detect the connection status of a load in a charging and discharging circuit. The charging and discharging circuit can be a DC-DC circuit including a DC-DC IC (DC-DC converter). Typically, DC-DC circuits have two topologies: a BUCK circuit (buck converter) and a BOOST circuit (boost converter).

[0028] When the charging and discharging circuit is a DC-DC BUCK circuit, such as Figure 2 As shown, the input terminal of the DC-DC IC is connected to the power supply VIN, the switching pin of the DC-DC IC is connected to the input terminal of the energy storage element, the output terminal of the energy storage element is connected to the input terminal of the load, and the output terminal of the load is grounded through the output terminal of the output capacitor. In this embodiment, the energy storage element can be an inductor. The common terminal of the switching pin of the DC-DC IC and the energy storage element can be referred to as SW1. Input capacitor C 输入 The input terminal is connected between the power supply VIN and the input terminal of the DC-DC IC, and the input capacitor C... 输入The output terminal is grounded. The ground pin of the DC-DC IC is grounded. Output capacitor C 输出 The input terminal is connected between the output terminal of the energy storage element and the input terminal of the load, and the output capacitor C 输出 The output terminal of diode D is connected to the output terminal of the load. The input terminal of diode D is connected to the output capacitor C. 输出 The output terminal of diode D is connected to the switching pin of the DC-DC IC and the common terminal SW1 of the energy storage element.

[0029] The load detection circuit may include a switching element, a first resistor, and a controller. The input terminal of the switching element is connected to the power supply VCC, and the second output terminal of the switching element is connected to the controller. The first output terminal of the switching element is connected to the input terminal of the first resistor, and the output terminal of the first resistor is connected to the common terminal SW1 of the switching pin of the DC-DC IC in the charging / discharging circuit and the energy storage element.

[0030] When the charging and discharging circuit is a DC-DC BUCK circuit, the working principle of the load detection circuit is as follows:

[0031] The DC-DC IC controls the switch, which has at least two states: on and off. When the switch in the DC-DC IC is on, the power supply VIN is applied to the DC-DC BUCK circuit. Current flows through the energy storage element, the output capacitor, and the load, and then to ground, forming a loop. Because the switch in the DC-DC IC is on, the voltage value of SW1 is the input value of the power supply VIN, which is high; the energy storage element is in the energy storage stage, and the output capacitor is in the charging stage.

[0032] When the switch in the DC-DC IC is turned off, the energy storage element releases energy, the output capacitor discharges, and current flows through the load, then through the diode back to SW1, forming a loop. At this time, the voltage across SW1 is the forward voltage drop of diode D, i.e., V. SW1 =-V D When the inductor has finished discharging, the voltage at SW1 is the output voltage, which is high.

[0033] SW1 transmits a level signal to the first output terminal of the switching element in the load detection circuit via the first resistor. When SW1 is low, the switching element is in the on state, and the second output terminal of the switching element transmits the first electrical signal output by the power supply VCC to the controller. When SW1 is high, the switching element is in the off state. The on and off states of the switch in the DC-DC IC cause SW1 to switch between high and low levels, thereby controlling the on and off states of the switching element in the load detection circuit.

[0034] The operating modes of a DC-DC IC include PFM (Pulse Frequency Modulation) mode. The operating modes of a DC-DC IC can also include a hybrid mode of PFM mode and a second modulation mode, such as PWM (Pulse Width Modulation). In this embodiment, the second modulation mode can be PWM mode. Therefore, the hybrid operating mode can be, for example, a hybrid mode of PFM and PWM.

[0035] When the DC-DC IC operates in PFM mode, it remains in PFM mode regardless of whether the load is under heavy or light load conditions. When the DC-DC IC operates in a mixed PFM and PWM mode, it operates in PWM mode under heavy load conditions and automatically switches to PFM mode under light load conditions.

[0036] After the DC-DC IC enters PFM mode, as the load capacity in the charging and discharging circuit decreases, the charging signal demanded by the load decreases, resulting in reduced energy consumption and current in the DC-DC BUCK circuit, and consequently, reduced power supply. Therefore, while the pulse width of the switch in the DC-DC IC remains constant, the pulse frequency decreases, and the period becomes longer, meaning the pulse interval between switches becomes longer. This change in the switching pulses in the DC-DC IC leads to a longer interval in the voltage change of SW1, which in turn causes a longer interval in the conduction of the switching elements in the load detection circuit, ultimately resulting in a smaller first electrical signal transmitted to the controller. Therefore, the first electrical signal transmitted to the controller decreases as the load capacity decreases.

[0037] The preset value can be the value of the second electrical signal when the load is at a preset capacity. The preset value can be a value set manually based on the type of load and actual conditions. For example, the preset value can be set to the value of the second electrical signal transmitted to the controller when the load capacity in the charging / discharging circuit is 20% of the rated load capacity; or, the preset value can be set to the value of the second electrical signal transmitted to the controller when the load current in the charging / discharging circuit is 50mA; or, when the load is a mobile phone battery, the preset value can be set to the value of the second electrical signal transmitted to the controller when the mobile phone battery reaches 95% of its full charge.

[0038] When the first electrical signal is less than a preset value, the load in the charging and discharging circuit can be in a light-load condition, and the controller sends a load disconnection command to the charging and discharging circuit. In this embodiment, the controller transmits a command to the enable pin of the DC-DC IC to turn off the DC-DC IC.

[0039] When the first electrical signal is less than a preset value, the load in the charging and discharging circuit can be in an unloaded state. The current required by the load when it is in an unloaded state is less than the current required by the load when it is in a light load state. The first electrical signal when the load is in an unloaded state is also less than the first electrical signal when the load is in a light load state, and is also less than the preset value. Therefore, when the first electrical signal is less than the preset value, the load in the charging and discharging circuit can be in an unloaded state, and the load in the charging and discharging circuit is in an open state.

[0040] When the load capacity in the charging / discharging circuit changes, the first electrical signal transmitted to the controller changes accordingly. A preset value is manually set based on the load type and actual conditions. When the first electrical signal value is less than the preset value, the controller sends a load disconnect command to the charging / discharging circuit, or the load in the charging / discharging circuit is disconnected.

[0041] When the charging and discharging circuit is a DC-DC BOOST circuit, such as Figure 3 As shown, the input terminal of the energy storage element is connected to the power supply VIN, the output terminal of the energy storage element is connected to the switch pin of the DC-DC IC, the output terminal of the DC-DC IC is connected to the input terminal of the load, and the output terminal of the load is grounded through the output terminal of the output capacitor. In this embodiment, the energy storage element can be an inductor. The common terminal of the switch pin of the DC-DC IC and the energy storage element can be referred to as SW2. Input capacitor C 输入 The input terminal is connected between the power supply VIN and the input terminal of the energy storage element, and the input capacitor C... 输入 The output terminal is grounded. The ground pin of the DC-DC IC is grounded. Output capacitor C 输出 The input terminal is connected between the output terminal of the DC-DC IC and the input terminal of the load, and the output capacitor C 输出 The output terminal is connected to the output terminal of the load. Diode D is connected in parallel with the DC-DC IC.

[0042] The load detection circuit may include a switching element, a first resistor, and a controller. The input terminal of the switching element is connected to the power supply VCC, and the second output terminal of the switching element is connected to the controller. The first output terminal of the switching element is connected to the input terminal of the first resistor, and the output terminal of the first resistor is connected to the common terminal SW2 of the DC-DC IC and the energy storage element in the charging / discharging circuit.

[0043] When the charging / discharging circuit is a DC-DC BOOST circuit, the working principle of the load detection circuit is as follows:

[0044] When the switch in the DC-DC IC is turned on, current flows through the energy storage element and then to ground, forming a loop. The energy storage element is in the energy storage phase. At this time, the voltage value of SW2 is close to 0V, which is a low level.

[0045] When the switch in the DC-DC IC is turned off, the energy storage element releases energy, and the current flows through diode D and the load, then to ground, forming a loop. At this time, the voltage value of SW2 is the sum of the diode forward voltage drop and the output voltage, which is a high level.

[0046] For a detailed explanation of the working principle, please refer to [the relevant documentation / reference]. Figure 2 The working principle of the load detection circuit based on the DC-DC Buck circuit shown is not described in detail here.

[0047] An embodiment of the load detection circuit based on a DC-DC BUCK circuit provided in this application is as follows: Figure 4 As shown. When the charging / discharging circuit is a DC-DC BUCK circuit, the DC-DC IC is a step-down DC-DC converter. The input terminal of the DC-DC IC is connected to the power supply VIN, the switch pin of the DC-DC IC is connected to the input terminal of inductor L, the output terminal of inductor L is connected to the input terminal of the load, and the output terminal of the load is grounded through the output terminal of the output capacitor. The common terminal of the switch pin of the DC-DC IC and the inductor L can be SW1. Input capacitor C 输入 The input terminal is connected between the power supply VIN and the input terminal of the DC-DC IC, and the input capacitor C... 输入 The output terminal is grounded. The ground pin of the DC-DC IC is grounded. Output capacitor C 输出 The input terminal is connected between the output terminal of inductor L and the input terminal of the load, and the output capacitor C... 输出 The output terminal of diode D is connected to the output terminal of the load. The input terminal of diode D is connected to the output capacitor C. 输出 The output terminal of diode D is connected to the common terminal SW1 of the DC-DC IC's switch pin and the inductor L. When the DC-DC IC includes synchronous rectification, diode D can be omitted (not shown in the figure).

[0048] The load detection circuit may include a switching element, a first resistor, and a controller. The switching element may be a transistor Q, such as a PNP transistor. The controller may be an MCU (Microcontroller Unit), such as a single-chip microcomputer. The emitter of transistor Q is connected to the power supply VCC, the base of transistor Q is connected to the input terminal of the first resistor, and the collector of transistor Q is connected to the single-chip microcomputer. The output terminal of the first resistor is connected to SW1.

[0049] The load detection circuit may also include a filtering circuit, which may include a filtering resistor and a filtering capacitor. The input terminal of the filtering resistor is connected to the collector of the transistor, and the output terminal of the filtering resistor is connected to the microcontroller. The input terminal of the filtering capacitor is connected between the filtering resistor and the microcontroller, and the output terminal of the filtering capacitor is grounded. The pulse signal from the transistor has a waveform with a constant pulse width but a period that varies with the load capacity. After passing through the filtering circuit, the first electrical signal received by the microcontroller also shows a change in the first electrical signal with the load capacity; that is, the smaller the load capacity, the smaller the charging signal required by the load, and the smaller the first electrical signal received by the microcontroller. The filtering circuit can smooth the pulse signal from the transistor, converting it into an approximate DC voltage. The filtering circuit can also eliminate high-frequency noise and protect the circuit from high-frequency interference.

[0050] The load detection circuit may also include a first capacitor, which is connected in parallel with a first resistor. The first capacitor can improve the switching speed of the transistor, thus accelerating the startup process.

[0051] The load detection circuit may also include a second resistor, with its input connected to the power supply VCC and its output connected to the emitter of a transistor. The second resistor can limit the pulse current passing through the transistor, effectively reducing the high-frequency ripple generated by the power supply VCC due to high-frequency pulses.

[0052] The controller may also include an ADC (analog-to-digital converter), with the output of the filter resistor connected to the ADC. The ADC can convert continuous electrical signals into discrete digital signals for storage and processing by the microcontroller.

[0053] Preset values ​​can be manually set according to the type of load and actual conditions. For example, the preset value can be set to the value of the second electrical signal transmitted to the controller when the load capacity in the charging and discharging circuit is 20% of the rated load capacity; or, the preset value can be set to the value of the second electrical signal transmitted to the controller when the load current in the charging and discharging circuit is 50mA; or, when the load is a mobile phone battery, the preset value can be set to the value of the second electrical signal transmitted to the controller when the battery power reaches 95% of its full charge.

[0054] When the first electrical signal received by the microcontroller is less than the preset value, the controller sends a load disconnect command to the charging and discharging circuit or the load in the charging and discharging circuit is in a disconnected state.

[0055] For a detailed explanation of the working principle, please refer to [the relevant documentation / reference]. Figure 2 The working principle of the load detection circuit based on the DC-DC Buck circuit shown is not described in detail here.

[0056] An embodiment of the load detection circuit based on the DC-DC BOOST circuit provided in this application is as follows: Figure 5 As shown. When the charging / discharging circuit is a DC-DC BOOST circuit, the DC-DC IC is a boost converter type DC-DC converter. The input terminal of inductor L is connected to the power supply VIN, the output terminal of inductor L is connected to the switch pin of the DC-DC IC, the output terminal of the DC-DC IC is connected to the input terminal of the load, and the output terminal of the load is grounded through the output terminal of the output capacitor. The common terminal of the switch pin of the DC-DC IC and the energy storage element can be SW2. Input capacitor C 输入 The input terminal is connected between the power supply VIN and the input terminal of the inductor L, and the input capacitor C... 输入 The output terminal is grounded. The ground pin of the DC-DC IC is grounded. Output capacitor C 输出 The input terminal is connected between the output terminal of the DC-DC IC and the input terminal of the load, and the output capacitor C 输出 The output terminal is connected to the output terminal of the load. Diode D is connected in parallel with the DC-DC IC. When the DC-DC IC includes synchronous rectification, diode D can be omitted (not shown in the figure).

[0057] The output terminal of the first resistor in the load detection circuit is connected to SW2.

[0058] The circuit structure of the load detection circuit in this embodiment is the same as that of the load detection circuit in the embodiment of the load disconnection detection circuit based on the DC-DC BUCK circuit. The working process of the load detection circuit in this embodiment is the same as that of the load disconnection detection circuit in the embodiment of the DC-DC BUCK circuit, and will not be described in detail here.

[0059] Current DC-DC ICs generally include a PFM (Power Flow Mode) operating mode. Using PFM mode when the load is lightly loaded or unloaded can reduce the power consumption of the DC-DC IC. This application utilizes the waveform characteristics of the charging and discharging circuit in the DC-DC IC under PFM mode; the first electrical signal changes with the load capacity. By comparing the first electrical signal with a preset value, the current load connection status can be detected. When the first electrical signal received by the controller is less than the preset value, the controller sends a load disconnect command to the charging and discharging circuit, or the load in the charging and discharging circuit is disconnected.

[0060] The load detection circuit provided in this application eliminates the sampling resistor and sampling amplification circuit in the prior art, reduces the internal resistance in the charging and discharging circuit, reduces the energy consumption in the circuit, improves the efficiency of the circuit loop, and also reduces the implementation cost of load detection.

[0061] Based on the above, this application also provides a charging and discharging circuit, including a charging and discharging circuit and the aforementioned load detection circuit.

[0062] Based on the above, this application also provides a mobile charging and discharging device, including: a housing, and a plurality of connection ports disposed on the housing. The plurality of connection ports are respectively used for connecting to a device to be charged, and for connecting the mobile charging device to a power supply when charging is required. A charging and discharging circuit is disposed within the housing, and the charging and discharging circuit includes the aforementioned load detection circuit.

[0063] Based on the above, this application also provides a solar charging and discharging device, including: a solar panel, and a charging and discharging device connected to the solar panel. The charging and discharging device includes a charging and discharging circuit, and the aforementioned load detection circuit.

[0064] Based on the above, this application also provides an off-grid solar energy system, including: a solar panel, a charging and discharging device, and an electronic device. The solar panel is connected to the charging and discharging device to convert the energy of the solar panel into electrical energy to charge the charging and discharging device. The charging and discharging device is used to store electrical energy and, when connected to the electronic device, to charge the electronic device. The charging and discharging device includes a charging and discharging circuit and the aforementioned load detection circuit.

[0065] Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of this application. Therefore, the scope of protection of this application should be determined by the scope defined in the claims of this application.

Claims

1. A load detection circuit, characterized by, The application is applied to detect the connection state of the load in the charge-discharge circuit, and the load detection circuit comprises a switching element, a first resistor and a controller. The input end of the switching element is connected to a power supply, and the output end of the switching element is connected to the controller. The input end of the first resistor is connected to the first output end of the switching element, and the output end of the first resistor is connected to the common end between the switching pin of the DC-DC converter and the energy storage element in the charge-discharge circuit. The DC-DC converter comprises a pulse frequency modulation working mode, in which the common end transmits a low-level signal to the first output end of the switching element through the first resistor, so that the switching element is in a conducting state, the second output end of the switching element transmits a first electric signal output by the power supply end to the controller, and the controller sends a load disconnection instruction to the charge-discharge circuit or the load in the charge-discharge circuit is in a disconnected state when the first electric signal is less than a preset value.

2. The load detection circuit of claim 1, wherein, The filter circuit comprises a filter resistor and a filter capacitor, the input end of the filter resistor is connected to the second output end of the switching element, the output end of the filter resistor is connected to the controller, the input end of the filter capacitor is connected between the filter resistor and the controller, and the output end of the filter capacitor is grounded.

3. The load detection circuit of claim 1, wherein, The preset value is the value of a second electric signal when the load is a preset capacity.

4. The load detection circuit of claim 1, wherein, The DC-DC converter comprises a step-down conversion type and a step-up conversion type. When the DC-DC converter is of the step-down conversion type, the output end of the first resistor is connected to the common end between the input end of the energy storage element and the switching pin. When the DC-DC converter is of the step-up conversion type, the output end of the first resistor is connected to the common end between the output end of the energy storage element and the switching pin.

5. The load detection circuit of claim 1, wherein, The first capacitor is connected in parallel with the first resistor.

6. The load detection circuit of claim 1, wherein, The second resistor is connected to the power supply, and the output end of the second resistor is connected to the input end of the switching element.

7. A charge-discharge circuit characterized by comprising: The application comprises: The charge-discharge circuit and the load detection circuit, wherein the load detection circuit is any one of the load detection circuits in claims 1-6.

8. A mobile charging and discharging device, characterized by, The application comprises a shell and a plurality of connection ports arranged on the shell. The plurality of connection ports are respectively used for connecting to a device to be charged and connecting the mobile charging device to a power supply when the mobile charging device needs to be charged, and the shell is provided with a charge-discharge circuit, and the charge-discharge circuit comprises the load detection circuit in any one of claims 1-6.

9. A solar charging and discharging device, characterized by, The application comprises: The application comprises a solar panel and a charge-discharge device connected to the solar panel, wherein the charge-discharge device comprises a charge-discharge circuit and the load detection circuit in any one of claims 1-6.

10. An off-grid solar system characterized in that, The application comprises: The solar panel, the charging and discharging device and the electronic equipment; the solar panel is connected with the charging and discharging device, is used for converting the energy of the solar panel into electric energy to charge the charging and discharging device, the charging and discharging device is used for storing the electric energy, and when connecting the electronic equipment, the electronic equipment is charged, the charging and discharging device includes a charging and discharging circuit and the load detection circuit as any one of claims 1-6.

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