A charging and discharging circuit supporting two series-connected nickel-metal hydride and lithium batteries

Abstract

The utility model relates to the field of rechargeable batteries, and specifically discloses a charging and discharging circuit that supports two nickel-metal hydride and lithium batteries connected in series, including a main control module, an external power socket, a buck-boost module, a logic control module, a lithium battery charging module, and a nickel-metal hydride battery charging module; the main control module controls the on and off of the lithium battery on-off unit and the nickel-metal hydride on-off unit in the logic control module through a single-chip microcomputer, and the logic control module switches whether the battery is charged or discharged according to whether the switch is turned on and whether the external power socket is powered on. The utility model provides a charging and discharging solution that can be directly compatible with two No. 5 nickel-metal hydride batteries or two No. 5 lithium batteries in the battery compartment structure of existing common dual No. 5 battery-powered products, so that the product does not need to change the mold of the battery compartment to distinguish the battery type, improves user experience, meets user needs, and makes the product more cost-effective.

Description

Technical Field

[0001] The utility model relates to the field of rechargeable batteries, in particular to a charging and discharging circuit supporting two nickel-hydrogen and lithium batteries connected in series. Background Art

[0002] At present, the charging and discharging circuits of NiMH batteries and lithium batteries on the market are mainly for single type of rechargeable batteries. In the field of wireless microphones, two No. 5 batteries are usually used for power supply. Under the premise that the battery compartment is not changed, the lithium battery is made into the size of two No. 5 batteries for compatibility, so that the two batteries can be directly replaced with each other. However, the voltage of two lithium batteries in series can be as high as 6.4V to 8.4V, while the voltage of two NiMH batteries in series is about 1.8v to 3V. The voltage difference between the two batteries can reach 3.4V to 5.4V in actual use.

[0003] The charging chips currently on the market cannot meet the voltage range of up to 1.8V to 8.4V when charging both NiMH batteries and lithium batteries. Therefore, the existing microphone solutions generally have the problem that two NiMH batteries and two lithium batteries cannot be directly replaced, which makes it impossible to meet the user's battery diversity needs. Utility Model Content

[0004] In order to overcome the problem that existing lithium batteries or nickel-metal hydride batteries are difficult to be compatible and interchangeable when two AA batteries are used in series, the utility model provides a charging and discharging circuit that supports two nickel-metal hydride and lithium batteries connected in series.

[0005] The technical solution adopted by the utility model is: a charging and discharging circuit supporting two nickel-metal hydride and lithium batteries connected in series, used for supplying power to electrical equipment, including a main control module, an external power socket, a buck-boost module, a logic control module, a lithium battery charging module and a nickel-metal hydride battery charging module;

[0006] The external power socket is used to connect to an external power supply;

[0007] The lithium battery charging module is used to connect to the power supply of the external power socket, and after boosting the voltage to the charging voltage required for the two lithium batteries connected in series, output it to the fifth output terminal;

[0008] The nickel-hydrogen battery charging module is used to connect to the power supply of the external power socket, and after reducing the voltage to the charging voltage required by two nickel-hydrogen batteries connected in series, output it to the sixth output terminal;

[0009] The main control module includes an MCU chip and its supporting peripheral circuits;

[0010] The logic control module includes a battery access terminal, a voltage sampling unit, a switch control unit, a charging switching unit, a lithium battery on-off unit and a nickel-metal hydride on-off unit;

[0011] The battery access terminal is used to connect the positive and negative electrodes of two nickel-metal hydride or lithium batteries connected in series;

[0012] The voltage sampling unit is connected in parallel with the battery access terminal, and is used to collect battery voltage data and output it to the third pin of the MCU chip;

[0013] The switch control unit comprises a first switch and a first cut-off circuit; the first cut-off circuit is provided with a first input terminal, a first output terminal and a first control terminal, the first input terminal is connected to the positive electrode of the battery access terminal; the two ends of the first switch are respectively connected to the first control terminal and the first input terminal; the first cut-off circuit is used to conduct the first input terminal and the first output terminal when the input voltage of the first control terminal is greater than the second threshold value, otherwise, the first input terminal and the first output terminal are disconnected;

[0014] The lithium battery on-off unit is provided with a third input terminal, a third output terminal and a third control terminal, the third input terminal is connected to the fifth output terminal, the third control terminal is connected to the first pin of the MCU chip, and the lithium battery on-off unit is used to switch the on-off between the third input terminal and the third output terminal according to the control signal of the third control terminal;

[0015] The nickel-metal hydride on-off unit is provided with a fourth input terminal, a fourth output terminal and a fourth control terminal, the fourth input terminal is connected to the sixth output terminal, the fourth control terminal is connected to the second pin of the MCU chip, and the nickel-metal hydride on-off unit is used to switch the on-off between the fourth input terminal and the fourth output terminal according to the control signal of the fourth control terminal;

[0016] The charging switching unit is provided with a second input terminal, a second output terminal and a second control terminal, the second control terminal is connected to the positive pole of the external power socket, the second input terminal is respectively connected to the first output terminal, the third output terminal and the fourth output terminal, and the second output terminal is respectively connected to the first control terminal and the input terminal of the buck-boost module; the charging switching unit is used to conduct the second control terminal and the second output terminal when the voltage of the second control terminal is greater than the first threshold; otherwise, conduct the second input terminal and the second output terminal;

[0017] The step-up / step-down module is used to step up / step-down the input voltage and output the voltage required for the main control module and the electrical equipment to work.

[0018] Preferably, the main control module includes a plurality of control buttons, and each of the control buttons is electrically connected to the MCU chip.

[0019] Preferably, the lithium battery charging module is provided with a first indicator light for displaying the working status of the lithium battery charging module, and the nickel-metal hydride battery charging module is provided with a second indicator light for displaying the working status of the nickel-metal hydride battery charging module.

[0020] Preferably, the voltage sampling unit comprises a first resistor and a second resistor, and the positive electrode of the battery access terminal, the first resistor, the third pin, the second resistor and the negative electrode of the battery access terminal are sequentially connected in series.

[0021] Preferably, the first switch is any one of a self-locking switch, a bridge switch and a toggle switch.

[0022] Preferably, the charging switching unit includes a second cutoff circuit and a third cutoff circuit;

[0023] The second cutoff circuit includes a seventh input terminal, a seventh output terminal and a seventh control terminal;

[0024] The third cutoff circuit comprises an eighth input terminal, an eighth output terminal and an eighth control terminal;

[0025] The second input terminal is connected to the seventh input terminal, the second output terminal is connected to the seventh output terminal and the eighth output terminal respectively, and the second control terminal is connected to the seventh control terminal, the eighth control terminal and the eighth input terminal respectively;

[0026] When the voltage of the second control terminal is less than or equal to the first threshold, the seventh output terminal and the seventh control terminal are turned on, and the eighth output terminal and the eighth control terminal are turned off; when the voltage of the second control terminal is greater than the first threshold, the seventh output terminal and the seventh control terminal are turned off, and the eighth output terminal and the eighth control terminal are turned on.

[0027] Preferably, the first cutoff circuit, the second cutoff circuit and the third cutoff circuit are all composed of emitter regions and collector regions of two transistors connected in reverse series.

[0028] Preferably, the second threshold is 1.5V, and the first threshold is 3V.

[0029] Preferably, the switch control unit further includes a shutdown circuit, one end of the shutdown circuit is connected to the fourth pin of the MCU chip, and the other end of the shutdown circuit is connected to the first control end.

[0030] The beneficial effects of the utility model are:

[0031] By providing a charging and discharging solution that can be directly compatible with two No. 5 nickel-metal hydride batteries or two No. 5 lithium batteries in the battery compartment structure of existing common dual No. 5 battery-powered products, the product does not need to change the mold of the battery compartment to distinguish the battery type, thereby improving the user experience, meeting user needs, and making the product more cost-effective. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention will be further described below in conjunction with the accompanying drawings, wherein:

[0033] Figure 1 This is a charging logic flow chart of the first embodiment of the utility model;

[0034] Figure 2 This is a circuit diagram of a logic control module of Embodiment 2 of the present utility model;

[0035] Figure 3 This is a circuit diagram of a step-up / step-down module according to Embodiment 2 of the present utility model;

[0036] Figure 4 This is a circuit diagram of the main control module of Embodiment 2 of the present utility model;

[0037] Figure 5 This is a circuit diagram of a nickel-hydrogen battery charging module according to Embodiment 2 of the present utility model;

[0038] Figure 6 This is a circuit diagram of a lithium battery charging module according to Embodiment 2 of the present utility model. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0040] The utility model aims to provide a circuit that supports charging and discharging of two nickel-metal hydride batteries or two lithium batteries connected in series, fully considering the compatibility of two nickel-metal hydride batteries and two lithium batteries connected in series, realizing diversified battery selection, and can be applied to wireless microphone power supply solutions and similar mobile devices with two No. 5 batteries for rechargeable power supply solutions, providing users with more battery compatibility.

[0041] See also Figure 1, is the first embodiment of the utility model, which specifically discloses a charging and discharging circuit that supports two nickel-metal hydride and lithium batteries connected in series, which is used to power electrical equipment, such as wireless microphones, radios, toy cars, remote controls and other electrical appliances with two AA battery compartments.

[0042] The circuit of this embodiment includes a main control module, an external power socket, a buck-boost module, a logic control module, a lithium battery charging module and a nickel-metal hydride battery charging module;

[0043] The external power socket is used to connect to the external power supply;

[0044] The lithium battery charging module is used to connect to the power supply of the external power socket, and after boosting the voltage to the required charging voltage of two lithium batteries connected in series, output it to the fifth output terminal;

[0045] The nickel-hydrogen battery charging module is used to connect to the power supply of the external power socket, and after reducing the voltage to the required charging voltage after two nickel-hydrogen batteries are connected in series, the voltage is output to the sixth output terminal;

[0046] The main control module includes an MCU chip and its supporting peripheral circuits; after the main control module is powered on, the battery detection is started, and the voltage output of the two batteries in series is detected through the third pin (VBAT_ADC) to determine whether it is two nickel-metal hydride batteries or two lithium batteries at this time, and the voltage is detected by ADC to determine whether it is a nickel-metal hydride battery or a lithium battery, and finally determine the relevant charging scheme. The MCU chip of this embodiment corresponds to the single-chip microcomputer chip U7 in the figure, and the specific model is ESP32-D0WD, which is used to control whether the output voltage of the lithium battery charging module and the nickel-metal hydride battery charging module is turned on, and judge whether the lithium battery or the nickel-metal hydride battery is currently used according to the data of the voltage sampling unit. The other functional peripherals not related to charging belong to the conventional design scheme in this field and are omitted in this embodiment.

[0047] The logic control module includes a battery access terminal, a voltage sampling unit, a switch control unit, a charging switching unit, a lithium battery on-off unit and a nickel-metal hydride on-off unit;

[0048] The battery access terminal is used to connect the positive and negative electrodes (BT1) of two nickel-metal hydride or lithium batteries connected in series, that is, the positive electrode (BT1-2) and negative electrode (BT1-1) of the battery compartment for installing two No. 5 batteries. In conventional low-voltage circuits, the negative electrode is usually grounded.

[0049] The voltage sampling unit is connected in parallel with the battery access terminal, and is used to collect data on the battery voltage and output it to the third pin (VBAT_ADC) of the MCU chip. The voltage sampling unit of this embodiment uses two resistors in series, that is, the voltage sampling unit includes a first resistor and a second resistor, and the positive pole of the battery access terminal, the first resistor, the third pin, the second resistor, and the negative pole of the battery access terminal are connected in series in sequence. The midpoint voltage between the two resistors is directly input into the pin of the MCU chip, so that when the positive and negative voltages of the two batteries in series are higher than 3.5V (i.e., lithium batteries) after the two batteries are connected in series, the single-chip microcomputer recognizes it as a high level, and when it is lower than 3.5V (i.e., nickel-hydrogen batteries), the single-chip microcomputer recognizes it as a low level, so that it can be determined whether it is a lithium battery or a nickel-hydrogen battery. In other embodiments, an ADC sampling circuit or a ready-made voltage sampling module can also be used to directly convert the voltage value into a digital signal that can be read by the single-chip microcomputer, so that the main control module can know the voltage of the current battery more specifically, which is convenient for adding a power display, or realizing functions such as preventing the battery from being overcharged or over-discharged, and intelligently adjusting the charging process (through PWM).

[0050] The switch control unit includes a first switch and a first cut-off circuit; the first cut-off circuit is provided with a first input terminal, a first output terminal and a first control terminal, the first input terminal is connected to the positive electrode of the battery access terminal; the two ends of the first switch are respectively connected to the first control terminal and the first input terminal; the first cut-off circuit is used to connect the first input terminal and the first output terminal when the input voltage of the first control terminal is greater than the second threshold, otherwise, disconnect the first input terminal and the first output terminal; the second threshold of this embodiment is 1.5V, which is used to judge whether the switch is turned on, so that the positive electrode of the battery is connected to the first control terminal, and when two nickel-hydrogen batteries (0.9v to 1.5V) are used for power supply, the battery voltage may output a voltage between 1.8v and 3V, that is, the voltage of the positive electrode of the battery must be greater than 1.5v; the first threshold is 3V, which is used to judge whether the external power socket is connected to a 5V power supply. Of course, in other embodiments, the first threshold and the second threshold can be reasonably increased or decreased according to the actual design of the circuit.

[0051] The lithium battery on-off unit is provided with a third input terminal, a third output terminal and a third control terminal, the third input terminal is connected to the fifth output terminal, the third control terminal is connected to the first pin of the MCU chip, and the lithium battery on-off unit is used to switch the on-off between the third input terminal and the third output terminal according to the control signal of the third control terminal. It is realized by controlling whether to output the voltage of the lithium battery charging module output (point A2) through the first pin (GPIO23) of the MCU.

[0052] The nickel-metal hydride on-off unit is provided with a fourth input terminal, a fourth output terminal and a fourth control terminal, the fourth input terminal is connected to the sixth output terminal, the fourth control terminal is connected to the second pin of the MCU chip, and the nickel-metal hydride on-off unit is used to switch the on-off between the fourth input terminal and the fourth output terminal according to the control signal of the fourth control terminal. It is realized to control whether to output the voltage of the nickel-metal hydride battery charging module output (point A1) through the second pin (GPIO2) of the MCU.

[0053] The charging switching unit is provided with a second input terminal, a second output terminal and a second control terminal, the second control terminal is connected to the positive pole of the external power socket, the second input terminal is respectively connected to the first output terminal, the third output terminal and the fourth output terminal, and the second output terminal is respectively connected to the first control terminal and the input terminal of the buck-boost module; the charging switching unit is used to connect the second control terminal and the second output terminal when the voltage of the second control terminal is greater than the first threshold; otherwise, the second input terminal and the second output terminal are connected.

[0054] The buck-boost module is used to boost or step down the input voltage and output the voltage required for the main control module and electrical equipment to work, specifically 3.3V DC power supply. The buck-boost module of this embodiment uses the power chip U6, model TPS63070RNMR, which supports 2-16V voltage input and 2.5-9V voltage output. It can meet the needs of powering two nickel-metal hydride batteries, two lithium batteries or a USB interface (external power socket) with 5V output. It can output 3.3V DC power to the main control module by boosting or stepping down, ensuring that the system can meet the needs of stable operation of the system under a variety of different power supply conditions.

[0055] Among them, the first switch SW9 can be any one of a self-locking switch, a bridge switch and a toggle switch, and can be kept in a connected or disconnected state to control whether the rechargeable battery is discharged. When connected to an external power supply, the first switch SW9 has no effect during charging regardless of whether it is connected.

[0056] The switch control unit also includes a shutdown circuit, one end of which is connected to the fourth pin (GPIO21) of the MCU chip, and the other end of which is connected to the first control terminal. When the entire circuit is in a battery-powered state, if the fourth pin outputs a high-level signal at this time, Q33 is turned on, so that the first control is grounded, thereby disconnecting Q7 and Q8, and then Q26 and Q25 are disconnected, that is, the first cut-off circuit is disconnected, and the battery power supply is stopped.

[0057] This embodiment uses the above-mentioned circuit for supporting two series-connected nickel-metal hydride and lithium batteries to charge and discharge. The specific logic for implementing the two series-connected nickel-metal hydride and lithium battery charging and discharging method is as follows:

[0058] S1, determine whether the external power socket is connected to a high level; if so, execute step S2, otherwise, execute step S3;

[0059] S2, the main control module controls the on and off of the lithium battery on and off unit and the nickel-metal hydride on and off unit according to the level feedback from the voltage sampling unit;

[0060] When the feedback is a high level, the lithium battery on-off unit is controlled to be turned on and the nickel-metal hydride on-off unit is turned off;

[0061] When the feedback is a low level, the lithium battery on-off unit is controlled to be disconnected and the nickel-hydrogen battery on-off unit is controlled to be turned on;

[0062] S3, determining whether the first switch is turned on, if so, executing step S4, otherwise, executing step S5;

[0063] S4, the switch control unit is turned on and the charging switching unit is turned on, so that the battery access end is connected to the buck-boost module, the buck-boost module works and outputs power to power on the main control module, the main control module controls the lithium battery on-off unit to be turned off, and controls the nickel-hydrogen on-off unit to be turned off;

[0064] S5. The charge and discharge circuit does not work.

[0065] This embodiment provides a charging and discharging solution that can be directly compatible with two No. 5 nickel-metal hydride batteries or two No. 5 lithium batteries in the battery compartment structure of existing common dual No. 5 battery-powered products, so that the product does not need to change the mold of the battery compartment to distinguish the battery type, thereby improving user experience, meeting user needs, and making the product more cost-effective.

[0066] See also Figures 2 to 6 , is the second embodiment of the utility model, the difference between this embodiment and the first embodiment is that the main control module includes a plurality of control buttons, each of which is electrically connected to the MCU chip, and is used to control the functions of the MCU chip and switch the control model, interrupt and restart the MCU chip, and other functions.

[0067] Figure 2 Among them, BT1 is a battery compartment with two AA batteries connected in series, which is used to install two AA battery-sized lithium batteries or two AA battery-sized NiMH rechargeable batteries.

[0068] Figure 4 It is the circuit diagram of the main control module of this embodiment. The chip U7 adopts the ESP32-D0WD single-chip computer. H1 is the interface of the BOOT button, which is used to connect a trigger switch to control the single-chip computer to enter the boot mode; CN1 is the serial communication interface; X1 is the external crystal oscillator, which is connected to the 44 and 45 ports of U7; U8 is an external storage chip with the model number of GD25Q32CT IG.

[0069] The lithium battery charging module of this embodiment is provided with a first indicator light (LED1) for displaying the working status of the lithium battery charging module, and the nickel-metal hydride battery charging module is provided with a second indicator light (LED2) for displaying the working status of the nickel-metal hydride battery charging module.

[0070] The charging switching unit of this embodiment includes a second cut-off circuit and a third cut-off circuit;

[0071] The second cutoff circuit includes a seventh input terminal, a seventh output terminal and a seventh control terminal;

[0072] The third cutoff circuit includes an eighth input terminal, an eighth output terminal and an eighth control terminal;

[0073] The second input terminal is connected to the seventh input terminal, the second output terminal is connected to the seventh output terminal and the eighth output terminal respectively, and the second control terminal is connected to the seventh control terminal, the eighth control terminal and the eighth input terminal respectively;

[0074] When the voltage of the second control terminal is less than or equal to the first threshold, the seventh output terminal and the seventh control terminal are turned on, and the eighth output terminal and the eighth control terminal are turned off; when the voltage of the second control terminal is greater than the first threshold, the seventh output terminal and the seventh control terminal are turned off, and the eighth output terminal and the eighth control terminal are turned on.

[0075] The first cutoff circuit, the second cutoff circuit and the third cutoff circuit are all composed of emitter regions and collector regions of two transistors connected in reverse series, and the base regions of the two transistors are connected to the control terminal to prevent the voltage at the high potential from flowing back to the low potential.

[0076] Preferably, the bases of the two transistors connected in reverse series are each provided with a transistor for controlling whether the bases are turned on. Figure 2 As shown, Q7, Q8, Q3, Q4, Q11, Q12, Q15, Q16, Q20, and Q21 transistors control Q26, Q25, Q24, Q23, Q28, Q27, Q30, Q29, Q32, and Q31 transistors in turn; Q26 and Q25, Q24 and Q23, Q28 and Q27, Q30 and Q29, and Q32 and Q31 control the on-off of the circuit in pairs, the purpose of which is to prevent the voltage at the high potential from flowing back to the low potential.

[0077] When the external power socket is not connected to an external power source: if the first switch SW9 is connected at this time, the battery voltage turns on Q7 and Q8, thereby turning on Q26 and Q25, and then turning on Q15 and Q16, and turning on Q30 and Q29, and the voltage at the battery access end is turned on to the buck-boost module, the buck-boost module works to output a 3.3V voltage, and the equipment including the main control module starts to work.

[0078] When the external power socket is connected to an external power supply: the external input 5V voltage turns on Q17, Q15 and Q16 are turned off, thereby turning on Q30 and Q29, turning on Q7 and Q8, and turning on Q26 and Q25; at the same time, the external input 5V voltage turns on Q20 and Q21, thereby turning on Q32 and Q31, and connecting point A3 to the external power socket, so that the buck-boost module is powered by the external power supply 5V and outputs a 3.3V voltage, and the equipment including the main control module starts to work.

[0079] At this time, press the first switch SW9. Since Q30 and Q29 are cut off, the battery voltage will not be conducted to the buck-boost module. The MCU chip determines the output voltage of the two No. 5 batteries connected in series at BT1 according to the third pin (VBAT_ADC). The lithium battery charging module and the nickel-metal hydride battery charging module start working and output charging voltage under the input of the external power socket.

[0080] When it is a lithium battery, the first pin (GPIO23) of the MCU chip outputs a high level, Q3 and Q4 are turned on, thereby controlling Q24 and Q23 to be turned on, and the lithium battery is connected to the voltage at point A2 to enter the charging mode;

[0081] When it is a nickel-metal hydride battery, the second pin (GPIO2) of the MCU chip outputs a high level, Q11 and Q12 are turned on, thereby controlling Q28 and Q27 to be turned on, and the nickel-metal hydride battery is connected to the voltage at point A1 to enter the charging mode.

[0082] Similarly, this solution can be applied to battery compartments of other types of batteries, or electrical equipment with single or multiple batteries connected in series or parallel, such as two No. 7 batteries, three No. 1 batteries in series, etc., by simply changing the size of components such as resistors in the solution according to the number of batteries connected in series, and it can be universally used without any creative work.

[0083] The above specific embodiments further describe the purpose, technical solutions and beneficial effects of the utility model in detail. It should be understood that the above are only specific embodiments of the utility model and are not intended to limit the protection scope of the utility model. It is particularly pointed out that for those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model should be included in the protection scope of the utility model.

Claims

1. A charging and discharging circuit supporting two nickel-metal hydride or lithium batteries connected in series, used to power electrical equipment, characterized in that: It includes a main control module, an external power socket, a buck-boost module, a logic control module, a lithium battery charging module and a nickel-metal hydride battery charging module; The external power socket is used to connect to an external power supply; The lithium battery charging module is used to connect to the power supply of the external power socket, and after boosting the voltage to the charging voltage required for the two lithium batteries connected in series, output it to the fifth output terminal; The nickel-hydrogen battery charging module is used to connect to the power supply of the external power socket, and after reducing the voltage to the charging voltage required by two nickel-hydrogen batteries connected in series, output it to the sixth output terminal; The main control module includes an MCU chip and its supporting peripheral circuits; The logic control module includes a battery access terminal, a voltage sampling unit, a switch control unit, a charging switching unit, a lithium battery on-off unit and a nickel-metal hydride on-off unit; The battery access terminal is used to connect the positive and negative electrodes of two nickel-metal hydride or lithium batteries connected in series; The voltage sampling unit is connected in parallel with the battery access terminal, and is used to collect battery voltage data and output it to the third pin of the MCU chip; The switch control unit comprises a first switch and a first cut-off circuit; the first cut-off circuit is provided with a first input terminal, a first output terminal and a first control terminal, the first input terminal is connected to the positive electrode of the battery access terminal; the two ends of the first switch are respectively connected to the first control terminal and the first input terminal; the first cut-off circuit is used to conduct the first input terminal and the first output terminal when the input voltage of the first control terminal is greater than the second threshold value, otherwise, the first input terminal and the first output terminal are disconnected; The lithium battery on-off unit is provided with a third input terminal, a third output terminal and a third control terminal, the third input terminal is connected to the fifth output terminal, the third control terminal is connected to the first pin of the MCU chip, and the lithium battery on-off unit is used to switch the on-off between the third input terminal and the third output terminal according to the control signal of the third control terminal; The nickel-metal hydride on-off unit is provided with a fourth input terminal, a fourth output terminal and a fourth control terminal, the fourth input terminal is connected to the sixth output terminal, the fourth control terminal is connected to the second pin of the MCU chip, and the nickel-metal hydride on-off unit is used to switch the on-off between the fourth input terminal and the fourth output terminal according to the control signal of the fourth control terminal; The charging switching unit is provided with a second input terminal, a second output terminal and a second control terminal, the second control terminal is connected to the positive pole of the external power socket, the second input terminal is respectively connected to the first output terminal, the third output terminal and the fourth output terminal, and the second output terminal is respectively connected to the first control terminal and the input terminal of the buck-boost module; the charging switching unit is used to conduct the second control terminal and the second output terminal when the voltage of the second control terminal is greater than the first threshold; otherwise, conduct the second input terminal and the second output terminal; The step-up / step-down module is used to step up / step-down the input voltage and output the voltage required for the main control module and the electrical equipment to work.

2. A charging and discharging circuit supporting two series-connected nickel-metal hydride or lithium batteries according to claim 1, characterized in that: The main control module includes a plurality of control buttons, and each of the control buttons is electrically connected to the MCU chip.

3. A charging and discharging circuit supporting two series-connected nickel-metal hydride or lithium batteries according to claim 1, characterized in that: The lithium battery charging module is provided with a first indicator light for displaying the working status of the lithium battery charging module, and the nickel-metal hydride battery charging module is provided with a second indicator light for displaying the working status of the nickel-metal hydride battery charging module.

4. A charging and discharging circuit supporting two series-connected nickel-metal hydride or lithium batteries according to claim 1, characterized in that: The voltage sampling unit includes a first resistor and a second resistor, and the positive electrode of the battery access terminal, the first resistor, the third pin, the second resistor and the negative electrode of the battery access terminal are sequentially connected in series.

5. A charging and discharging circuit supporting two series-connected nickel-metal hydride or lithium batteries according to claim 1, characterized in that: The first switch is any one of a self-locking switch, a bridge switch and a toggle switch.

6. A charging and discharging circuit supporting two series-connected nickel-metal hydride or lithium batteries according to claim 1, characterized in that: The charging switching unit includes a second cut-off circuit and a third cut-off circuit; The second cutoff circuit includes a seventh input terminal, a seventh output terminal and a seventh control terminal; The third cutoff circuit comprises an eighth input terminal, an eighth output terminal and an eighth control terminal; The second input terminal is connected to the seventh input terminal, the second output terminal is connected to the seventh output terminal and the eighth output terminal respectively, and the second control terminal is connected to the seventh control terminal, the eighth control terminal and the eighth input terminal respectively; When the voltage of the second control terminal is less than or equal to the first threshold, the seventh output terminal and the seventh control terminal are turned on, and the eighth output terminal and the eighth control terminal are turned off; When the voltage of the second control terminal is greater than the first threshold, the seventh output terminal and the seventh control terminal are disconnected, and the eighth output terminal and the eighth control terminal are connected.

7. A charging and discharging circuit supporting two series-connected nickel-metal hydride or lithium batteries according to claim 6, characterized in that: The first cutoff circuit, the second cutoff circuit and the third cutoff circuit are all composed of emitter regions and collector regions of two triodes connected in reverse series.

8. A charging and discharging circuit supporting two series-connected nickel-metal hydride or lithium batteries according to claim 1, characterized in that: The second threshold is 1.5V, and the first threshold is 3V.

9. A charging and discharging circuit supporting two series-connected nickel-metal hydride or lithium batteries according to claim 1, characterized in that: The switch control unit also includes a shutdown circuit, one end of which is connected to the fourth pin of the MCU chip, and the other end of which is connected to the first control end.

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