TW202505839A - Battery management circuit - Google Patents

Abstract

A battery management circuit is provided. The battery management circuit includes: a charging circuit, a discharging circuit and a control circuit. One end of the charging circuit is connected to the charging terminal of the battery to receive the charging signal, and the other end is connected to the positive electrode of the battery cell to provide charging voltage to the battery cell. One end of the discharging circuit is connected to the positive electrode of the battery cell to receive the discharge signal, and the other end is connected to the power supply end of the battery to provide the power supply voltage. The control circuit is connected to the selection terminal of the battery, and controls the states of the charging circuit and the discharging circuit according to the voltage of the selection terminal.

Description

Battery management circuit

The present invention relates to the field of battery technology, and in particular to a battery management circuit.

Batteries are roughly divided into primary batteries and secondary batteries. Primary batteries are non-rechargeable disposable batteries, such as carbon zinc batteries and alkaline batteries; secondary batteries are also called rechargeable batteries, which can be recharged repeatedly for use, such as nickel hydrogen batteries, lithium ion (Li-ion) batteries and lithium polymer (Li-polymer) batteries. At present, rechargeable batteries have gradually become the mainstream because they can meet diverse usage needs, and battery charging and discharging management has become increasingly important.

In view of this, the present invention provides a battery management circuit to achieve battery charge and discharge management at a relatively low cost.

Specifically, the technical solution of the present invention is as follows:

In a first aspect, the present invention provides a battery management circuit, comprising:

A charging circuit, one end of which is connected to the charging end of the battery to receive a charging signal, and the other end of which is connected to the positive electrode of the battery cell to provide a charging voltage to the battery cell;

A discharge circuit, one end of which is connected to the positive electrode of the battery cell to receive a discharge signal, and the other end of which is used to connect to the power supply terminal of the battery to provide a power supply voltage;

The control circuit is connected to the selection end of the battery and controls the state of the charging circuit and the discharging circuit according to the voltage of the selection end.

This embodiment provides a battery at a newly added selection end that switches the charging state and discharging state of the secondary battery through a signal received at the selection end.

In some embodiments of the battery management circuit, the control circuit includes:

A first voltage detector, wherein an input terminal of the first voltage detector is connected to a selection terminal of the battery, and when a voltage at the selection terminal is greater than or equal to a threshold voltage of the first voltage detector, an output terminal of the first voltage detector outputs a first voltage;

The first switch circuit is connected to the output end of the first voltage detector. When the output end of the first voltage detector outputs the first voltage, the first switch circuit is turned on. The first switch circuit is connected to the charging circuit. When the first switch circuit is turned on, the charging circuit is turned on.

This embodiment provides a component composition structure of a control circuit and a judgment logic for the control circuit to use these components to control the on and off of a charging circuit.

In some implementations of the battery management circuit, the threshold voltage of the first voltage detector is greater than the maximum supply voltage of the battery.

This embodiment provides a threshold voltage of the first voltage detector.

In some embodiments of the battery management circuit, the control circuit further comprises:

A second voltage detector, wherein an input end of the second voltage detector is connected to a charging end of the battery, and when a voltage at the charging end is greater than or equal to a threshold voltage of the second voltage detector, an output end of the second voltage detector outputs a second voltage;

The second switch circuit is connected to the output end of the second voltage detector. When the output end of the second voltage detector outputs the second voltage, the second switch circuit is turned on. The second switch circuit is connected to the discharge circuit. When the second switch circuit is turned on, the discharge circuit is turned on.

This embodiment provides a component structure of a control circuit and a judgment logic for the control circuit to control the on and off of a discharge circuit using this component structure.

In some battery management circuit implementations, this also includes:

A negative temperature coefficient thermistor has one end connected to the selected end of the battery and the other end connected to ground.

This embodiment provides a mounting position for the thermistor.

In some embodiments of the battery management circuit, the discharge circuit includes:

The adjusting sub-circuit is used to adjust the output voltage of the discharge circuit, wherein when the discharge signal of the battery cell is in a first range, the adjusting sub-circuit adjusts the discharge circuit to output the supply voltage with a first value, and when the discharge signal of the battery cell is in a second range, the adjusting sub-circuit adjusts the discharge circuit to output the supply voltage with a second value, and the first value is less than the second value.

This embodiment provides an adjustment sub-circuit that adjusts the output voltage by monitoring the discharge signal size of the battery cell.

In some embodiments of the battery management circuit, the regulating subcircuit includes:

A dual voltage comparator includes a first input terminal, a second input terminal, a third input terminal and an output terminal, wherein:

The first input terminal is connected to the positive electrode of the battery cell;

The second input terminal is connected to the positive electrode of the battery cell through a first resistor;

The third input terminal is connected to the positive electrode of the battery cell through the first resistor and the second resistor, and is grounded through the third resistor;

The third switch circuit is connected to the output end of the dual voltage comparator and is turned on or off under the control of the output voltage of the output end, wherein when the third switch circuit is turned on, the discharge circuit outputs the supply voltage having a first value, and when the third switch circuit is turned off, the discharge circuit outputs the supply voltage having a second value.

This embodiment provides a component connection structure for adjusting a sub-circuit and a component for controlling a supply voltage through a dual voltage comparator.

In some embodiments of the battery management circuit, the discharge circuit further comprises:

The buck converter includes an input terminal, an enable terminal, a feedback terminal, and an output terminal, wherein:

The input end is connected to the positive electrode of the battery cell;

The enable terminal disables the buck converter when the charging circuit is turned on, and enables the buck converter when the discharging circuit is turned on;

A fourth resistor and a fifth resistor are connected in parallel between the feedback terminal and the output terminal and are grounded via a sixth resistor. The fifth resistor is connected in series with the third switch circuit.

This embodiment provides a port composition and enable control logic for a buck converter.

In some implementations of the battery management circuit, the enable terminal is connected to the control circuit via a diode and is connected to the positive electrode of the battery cell via a seventh resistor.

In some embodiments of the battery management circuit, the buck converter further includes an output status indicator terminal, and the discharge circuit further includes:

The fourth switch circuit is located on the output path of the discharge circuit and is connected to the output state indication terminal of the buck converter.

In a second aspect, the present invention provides a battery, comprising a battery cell and a battery management circuit.

In some battery implementations, the method further includes:

The battery cell and the battery management circuit are arranged in the shell, and the charging end and the selection end of the battery are the first metal electrode and the second metal electrode on the shell.

In a third aspect, the present invention provides a charger, comprising:

A charging body having a receiving area for receiving a battery;

The first metal electrode and the second metal electrode are arranged in the containing area, the first metal electrode is used to provide a charging signal to the charging end of the battery, and the second metal electrode is used to provide a voltage to the selected end of the battery.

The above scheme introduces a selection terminal and a control circuit into the battery, and the control circuit uses the voltage of the selection terminal to control the state of the charging circuit or the discharging circuit, thereby turning on the charging circuit or the discharging circuit, realizing the management of battery charging and discharging with lower complexity, thereby reducing the cost of the battery.

In order to more clearly describe the embodiments of the present invention or the technical solutions in the prior art, the specific implementation of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings and other implementations can be obtained based on these accompanying drawings without creative labor.

In order to simplify the drawings, only the parts related to the present invention are schematically shown in each of the drawings, and they do not represent the actual structure of the product. In addition, in order to simplify the drawings and facilitate understanding, only one of the elements or components with the same structure or function is schematically shown in some drawings. In this article, "one" not only means "only one", but also means "more than one".

In this document, unless otherwise clearly specified or limited, the terms “connected” and “connected” should be understood in a broad sense. For example, it can be an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium (for example, other components).

In addition, in the description of the present invention, the terms "first", "second", etc. are only used to distinguish and describe related objects, and cannot be understood as indicating or implying the relative importance or order between related objects, nor do they represent the number of related objects.

As an energy supply device, batteries have been widely used in people's lives. Battery cells can be assembled into different devices to power them, such as small household appliances and portable electronic devices. For example, battery cells can be assembled into battery packs to power large devices such as electric vehicles.

Rechargeable batteries are widely used because they can be repeatedly charged and used, which can improve battery utilization, reduce costs, and are environmentally friendly. The present invention takes into account the charge and discharge management of rechargeable batteries and proposes a battery management circuit that manages battery charge and discharge with low complexity to reduce battery costs.

The following is a description with the attached pictures:

In one embodiment, referring to Figure 1 of the specification, an embodiment of the present invention provides a battery, which includes a case 110, a battery cell 120, and a circuit board 130. The circuit board 130 is provided with a battery management circuit for performing charge and discharge management on the battery, that is, performing charge and discharge management on the battery cell 120.

In one embodiment, a first metal electrode 111 and a second metal electrode 112 (hereinafter referred to as the first electrode and the second electrode) are disposed on the battery housing 110. The first electrode 111 is the positive electrode (V+) of the battery, receives the charging signal during charging, and provides the charging voltage to the positive electrode (B+) 121 of the battery cell 120 after being processed by the management circuit; and provides the supply voltage to the load of the battery during discharging. The second electrode 112 is the selection electrode (abbreviated as Sel electrode) of the battery, and the voltage on the Sel electrode is used as the selection voltage to control the charging and discharging state of the battery (or battery cell).

The battery cell 120 is disposed in the housing 110, and the positive electrode 121 of the battery cell 120 is connected to the positive electrode 111 of the battery through a management circuit. When the battery is in a charging state, the battery cell 120 receives a charging signal through the positive electrode 111 of the battery and is then charged; when the battery is in a discharging state, the battery cell 120 outputs a discharging signal and provides a supply voltage through the positive electrode 111 of the battery.

In the battery, the charging end and the power supply end of the battery are the same, which is the positive electrode 111 of the battery, and the battery management circuit is located in the battery shell 110, so that the power supply of small devices has low complexity and cost, and it is convenient to replace the battery. In other embodiments, the charging end and the power supply end of the battery can also be different; the battery management circuit can also be located outside the shell where the battery cell is located.

The management circuit on the circuit board 130 is described below. Please refer to Figure 2 of the specification. In the figure, V+ and V- represent the positive and negative electrodes of the battery respectively, and B+ and B- represent the positive and negative electrodes of the battery cell respectively. When charging, the positive electrode V+ of the battery can be the charging end of the battery; when discharging, the positive electrode of the battery can be the power supply end of the battery. For the convenience of description, the charging end and the power supply end of the battery are both represented by the positive electrode V+ of the battery. In other embodiments, they can also be different ports. In the figure, Sel represents the selection end of the battery. For example, in one embodiment, it can be the selection electrode shown in Figure 1. The management circuit 200 includes a charging circuit 210, a discharging circuit 220, and a control circuit 230. One end of the charging circuit 210 is connected to the charging terminal V+ of the battery to receive the charging signal, and the other end is connected to the positive electrode B+ of the battery cell to provide a charging voltage to the battery cell; one end of the discharging circuit 220 is connected to the positive electrode B+ of the battery cell to receive the discharging signal, and the other end is connected to the supply terminal V+ of the battery to provide a supply voltage; the control circuit 230 is connected to the selection terminal Sel of the battery, and controls the state of the charging circuit 210 or the discharging circuit 220 according to the voltage of the selection terminal Sel, for example, controlling the charging circuit 210 to be turned on and the discharging circuit 220 to be turned off; or controlling the discharging circuit 220 to be turned on and the charging circuit 210 to be turned off.

It can be seen that in the above embodiment, the control circuit 230 uses the voltage of the selection terminal Sel of the battery to control the state of the charging circuit 210 and the discharging circuit 220, thereby turning on the charging circuit 210 or the discharging circuit 220, and realizing the management of battery charging and discharging with lower complexity, thereby reducing the cost of the battery.

In one embodiment of the present invention, as shown in FIG1 , a selector 112 is added to the battery, and a control circuit 230 is connected to the selector 112, and the charging circuit 210 or the discharging circuit 220 is turned on according to the voltage on the selector 112. Furthermore, a selector can also be provided on the battery charger, and when the battery is placed on the charger for charging, the selector of the charger is connected to the selector 112 of the battery, providing the selector voltage V _sel to the selector 112 of the battery, thereby turning on the charging circuit 210.

In another embodiment of the present invention, as shown in the dotted frame in FIG. 2 , the control circuit 230 is connected to the positive electrode V+ of the battery through a resistor R, and the charging voltage forms a voltage drop through the resistor R to obtain a selection voltage _Vsel provided to the control circuit 230 to turn on the charging circuit 210. At this time, the selection terminal Sel does not need to be led out as an electrode, and there is no need to add a selection electrode to the charger, so that the management of battery charging and discharging can be achieved.

The above control circuit 230 can be implemented by using a comparator and a switch circuit, wherein the comparator is used to compare the voltage of the selection terminal Sel with the reference voltage. When the voltage of the selection terminal Sel is higher than the reference voltage, a high level or a low level is output, and the high level or the low level is used to turn on the switch circuit, and the switch circuit is used to turn on the charging circuit 210. At this time, the reference voltage is greater than the supply voltage range when the battery is discharged, that is, greater than the maximum supply voltage. The control circuit 230 may also include other components, such as resistors, transistors, etc., which cooperate with the comparator to enable the control circuit 230 to obtain better performance.

In some embodiments, the control circuit 230 uses a voltage detector and a switch circuit to turn on or off the charging circuit 210. The following is a description with reference to the accompanying drawings:

As shown in FIG. 3 , in one embodiment, the control circuit 230 includes a voltage detector U1 (which may be referred to as a first voltage detector) and a switch circuit S1 (which may be referred to as a first switch circuit). The input terminal Vin of the voltage detector U1 is connected to the selection terminal Sel of the battery, and when the voltage of the selection terminal Sel is greater than or equal to the threshold voltage of the voltage detector U1, the output terminal V _OUT of the voltage detector U1 outputs a first voltage; the switch circuit S1 is connected to the output terminal V _OUT of the voltage detector U1, and when the output terminal V _OUT of the voltage detector U1 outputs the first voltage, the switch circuit S1 is turned on, wherein the switch circuit S1 is connected to the charging circuit 210, and when the switch circuit S1 is turned on, the charging circuit 210 is turned on. The first voltage can be a high level or a low level, and correspondingly, the switch circuit S1 can be turned on at a high level or at a low level.

The threshold voltage of the voltage detector U1 can also be called a critical voltage. The threshold voltage can be set as needed, and the threshold voltage is greater than the supply voltage range when the battery is discharged, that is, greater than the maximum supply voltage. For example, when the supply voltage range of the battery is 1V-1.5V, the threshold voltage is greater than 1.5V, for example, it can be 1.8V. In one embodiment, when a selector electrode is added to the battery and the charger, the voltage provided by the selector electrode of the charger may be between 1.8V and 3.6V. When charging, the charger provides a select voltage between 1.8V and 3.6V to the selector electrode of the battery; when discharging or not connected to the charger, the selector electrode of the battery is floating or unconnected.

When the voltage detector U1 is working, when the input voltage (V _in ) of the voltage detector U1 is higher than the detection voltage (-V _DET ), the input voltage is equal to the output voltage (V _OUT ). When the input voltage (V _in ) is lower than the detection voltage (-V _DET ), the output voltage is equal to the ground potential. When the input voltage rises from the ground potential, when the input voltage (V _in ) is lower than the minimum operating voltage (V _min ), the output voltage is uncertain. When the input voltage (V _in ) exceeds the minimum operating voltage (V _min ), the output voltage will remain at a low level. When the input voltage rises to the release voltage (+V _DET ), the output voltage equals the input voltage. The voltage difference between the release voltage (+V _DET ) and the detection voltage (-V _DET ) is the hysteresis voltage. When the input voltage (V _in ) rises from the ground potential, the delay capacitor in the voltage detector U1 will produce a certain delay time. After the input voltage (V _in ) exceeds the release voltage (+V _DET ), it will take a certain delay time for the output voltage (V _OUT ) to equal the input voltage (V _in ).

The above threshold voltage includes a detection voltage or a release voltage, and the detection voltage has a typical value (typ), a maximum value (max), and a minimum value (min). The voltage of the above selection terminal Sel is greater than the threshold voltage of the voltage detector U1, and may include any voltage value greater than the detection voltage within the range from the minimum value to the maximum value (including the boundary), or greater than the release voltage (+V _DET ).

In one embodiment of the present invention, the control circuit 230 may further include a voltage detector U2 (which may be referred to as a second voltage detector) and a switch circuit S2 (which may be referred to as a second switch circuit) for controlling the on and off of the discharge circuit 220. Similarly, the input end of the voltage detector U2 is connected to the charging end V+ of the battery, and when the voltage at the charging end V+ is greater than or equal to the threshold voltage of the voltage detector U2, the output end of the voltage detector U2 outputs a second voltage; the switching circuit S2 is connected to the output end of the voltage detector U2, and when the output end of the voltage detector U2 outputs the second voltage, the switching circuit S2 is turned on; wherein, the switching circuit S2 is connected to the discharge circuit 220, and when the switching circuit S2 is turned on, the discharge circuit 220 is turned on.

The description of the voltage detector U2 refers to the voltage detector U1, and the threshold voltage of the voltage detector U2 is higher than the maximum supply voltage of the battery, and can be the same as or different from the threshold voltage of the voltage detector U1, but the switch circuit S2 has a different conduction logic from the switch circuit S1. For example, when the switch circuit S1 is high-level conduction, the switch circuit S2 is low-level conduction; when the switch circuit S1 is low-level conduction, the switch circuit S2 is high-level conduction.

For example, when the charging voltage is 4.2V, the threshold voltages of the voltage detectors U1 and U2 are both 1.8V, and the switch circuit S1 is turned on at a high level, and the switch circuit S2 is turned on at a low level: When charging, the charger provides a charging signal to the positive electrode of the battery, and the voltage detector U2 detects the charging signal, and the voltage value is higher than the threshold value of the voltage detector U2. voltage, then the second voltage (assuming a high level) is output, the switch circuit S2 is turned off, and the discharge circuit 220 is turned off; correspondingly, the voltage detector U1 detects the selected voltage, and the selected voltage is higher than the threshold voltage of the voltage detector U1, then the first voltage (assuming a high level) is output, the switch circuit S1 is turned on, and the charging circuit 210 is turned on.

In one embodiment of the present invention, the above discharge circuit 220 is a step-down circuit, that is, the output voltage of the discharge circuit 220 is lower than the input voltage. The discharge signal provided by the positive electrode B+ of the battery cell obtains a stepped-down voltage after passing through the discharge circuit 220; the discharge circuit 220 provides the stepped-down voltage to the power supply end of the battery for discharge.

The output voltage of traditional primary batteries (such as carbon zinc batteries, alkaline batteries, etc.) and nickel-hydrogen batteries is usually around 1.0V to 1.5V, while the output voltage of lithium batteries is often around 2.5V to 4.2V. Through the above step-down circuit, lithium cells can be stepped down to supply power, which combines the advantages of lithium batteries and meets the use requirements of traditional small household appliances.

In some embodiments of the present invention, as shown in FIG. 1 and FIG. 2 , the above battery may further include a thermistor RT, which is a negative temperature coefficient (NTC) thermistor, one end of which is connected to the selection end Sel of the battery, and the other end is grounded or connected to the negative pole of the cell (or battery). NTC thermistor is a kind of sensor resistor whose resistance value decreases as the temperature increases. In this way, the NTC thermistor is used to monitor the temperature of the battery during the battery charging process. As the temperature rises, the current in the branch where the thermistor RT is located increases. In conjunction with the pull-up resistor of the branch where the thermistor RT is located, the voltage of the selection terminal Sel decreases. When it decreases to below the threshold voltage of the control circuit 230 (for example, the threshold voltage of the voltage detector U1), the control circuit 230 turns off the charging circuit 210, thereby stopping the charging of the battery cell.

The above thermistor RT can be set in the battery or in the charger. For example, when the battery is provided with a selector Sel, a resistor can be set between the selector Sel and the thermistor RT; or a resistor can be set in the branch where the selector of the charger is located. When the selector Sel of the battery is connected to the selector of the charger, the thermistor RT is connected in series with the resistor set in the charger to form a branch through which the current flows; for another example, when the scheme shown in the virtual box in Figure 2 is adopted, the resistor R and the resistor RT are connected in series between the positive and negative electrodes (or the ground terminal) of the battery.

In the embodiment of the present invention, an NTC thermistor connected to the selection terminal Sel can be provided in the battery (for example, near the battery cell). The thermistor RT is used to monitor the temperature of the battery (or battery cell). As the temperature of the battery (or battery cell) increases, the resistance of the thermistor RT decreases, and the current in the branch where it is located increases, so that the voltage of the selection terminal Sel decreases. When the temperature of the battery (or battery cell) exceeds the preset temperature (corresponding to the threshold voltage of the control circuit 230), the control circuit 230 will stop charging the battery cell, thereby reducing the occurrence of battery damage caused by overheating of the battery cell. This implementation method realizes safety protection of the battery cell charging process with a simple and low-cost design. At this time, the selection terminal Sel can also be called the thermistor terminal.

In other embodiments of the present invention, the thermistor RT may be connected to other positions as long as the charging circuit 210 can be turned off when the battery cell temperature is too high. For example, a switch circuit is provided in the charging circuit 210, the thermistor RT is connected to the positive electrode of the battery through at least one resistor, and the voltage drop across the thermistor RT or the voltage at one end of the thermistor RT close to the positive electrode of the battery is used to control the on and off of the switch circuit in the charging circuit 210.

In one embodiment of the present invention, the discharge circuit 220 may further include an adjusting sub-circuit 221 for adjusting the output voltage V _out of the discharge circuit 220. Specifically, when the discharge signal of the battery cell is within the first range, the adjusting sub-circuit 221 adjusts the discharge circuit 220 to output a supply voltage having a first value; and when the discharge signal of the battery cell is within the second range, the adjusting sub-circuit 221 adjusts the discharge circuit 220 to output a supply voltage having a second value, and the first value is less than the second value. In other words, the adjusting sub-circuit 220 can further reduce the output voltage V _out of the discharge circuit 220 according to the discharge signal of the battery cell.

In this way, a mechanism of "lowering the voltage in advance" can be introduced when the battery energy has not reached the exhaustion standard. This mechanism can be understood as a buffer mechanism, which can notify the user or the load device behind the battery in advance that the battery power is low and is about to be exhausted, so that the user can take measures in advance, such as saving data, replacing the battery, charging, or shutting down, etc., to reduce the risk of losing data or damaging the load device. For example, the power light or indicator light of some small household appliances begins to flash to remind the user that the battery power is low; for another example, the load device automatically saves data, and can further perform the above reminder operations, and the above reminders can also be replaced by other reminder modes such as voice reminders and visual reminders.

In traditional batteries, the buck converter steps down the cell voltage for output without any buffer mechanism. When the cell voltage is less than the minimum allowable input voltage of the buck converter or the lock voltage of the cell protector, the output of the buck converter will immediately become "0", that is, the battery supply voltage will quickly drop to "0", and the load device may lose power without warning, and data may not be saved in time, resulting in data loss. In the long run, it may even cause damage to the load device.

In one embodiment, the above adjustment sub-circuit 221 is implemented using a dual voltage comparator. Specifically, as shown in FIG3 , the adjustment sub-circuit 221 includes a dual voltage comparator U3 and a switch circuit S3 (also referred to as a third switch circuit), and the dual voltage comparator U3 includes a first input terminal VDD, a second input terminal LTH, a third input terminal HTH, and an output terminal V _OUT . The first input terminal VDD can also be called the power supply input terminal, which is connected to the positive electrode B+ of the battery cell; the second input terminal LTH can also be called the low voltage threshold terminal, which is used to connect to the positive electrode B+ of the battery cell through the resistor R1 (or the first resistor); the third input terminal HTH can also be called the high voltage threshold terminal, which is connected to the positive electrode B+ of the battery cell through the resistor R1 and the resistor R2 (or the second resistor), and is connected to the negative electrode B- of the battery cell or ground (GND) through the resistor R3 (or the third resistor). The switch circuit S3 is connected to the output terminal V _OUT of the dual voltage comparator U3, and is turned on or off under the control of the output voltage of the output terminal V _OUT . When the switch circuit S3 is turned on, the discharge circuit 220 outputs a supply voltage with a first value, and when the switch circuit S3 is turned off, the discharge circuit 220 outputs a supply voltage with a second value.

The working principle of the dual voltage comparator is described below in conjunction with the attached figures. Please refer to FIG4, which is a schematic diagram of a dual voltage comparator chip. The dual voltage comparator 400 includes a first input terminal (power supply terminal) VDD, a second input terminal (low voltage threshold terminal) LTH, a third input terminal (high voltage threshold terminal) HTH, an output terminal OUT and a ground terminal GND, and the output terminal is connected to a pull-up resistor RPU, coupled to a pull-up voltage V _PULL-UP . The dual voltage comparator 400 can convert the input signal V _IN into two voltage thresholds (voltage threshold) V _HI and V _LO through external resistors R41, R42 and R43, which are respectively called upper edge voltage and lower edge voltage. These two voltages can be used to compare and detect voltages within a certain range. The upper voltage is also called the high voltage threshold, and the lower voltage is also called the low voltage threshold, which is calculated using the following formulas (1) and (2):

V _HI =V _REF (1)

V _LO =V _REF ( ) (2)

Wherein, V _REF is a reference voltage having a preset value; for example, in a dual voltage comparator chip, it is 1.24V.

As shown in Figure 5, when the detected voltage reaches the upper edge voltage V _HI , the output terminal OUT will output a high level, and when the detected voltage reaches the lower edge voltage V _LO , the output terminal OUT will output a low level, wherein the spike (short transient change) in Figure 5 will be ignored by the chip. When the dual voltage comparator 400 is used in a digital circuit, the logic signal can be processed as a hysteresis delay. In this embodiment, the dual voltage comparator 400 can adjust two voltage thresholds V _HI and V _LO to monitor V _IN through three external resistors to form a hysteresis curve characteristic, and then change the output voltage through this characteristic. Specifically, when the output voltage of the battery cell changes, the voltages of the input terminals LTH and HTH change accordingly. When the upper edge voltage V _HI is touched, the output terminal OUT will output a high level. When the lower edge voltage V _LO is touched, the output terminal OUT will output a low level. This can change the state of the switch circuit S3 connected thereto, thereby changing the resistance value of the discharge circuit 220, causing the output voltage to change.

Continuing to refer to FIG. 3 , the discharge circuit 220 can realize a buck output through a buck converter U4. The buck converter U4 includes an input terminal Vin, an enable terminal EN, a feedback terminal FB, and an output terminal SW. The input terminal Vin is used to connect to the positive electrode B+ of the battery cell; the enable terminal EN is used to enable or disable the buck converter U4, and when the charging circuit 210 is turned on, the enable terminal EN disables the buck converter U4, and when the discharge circuit (220) is turned on, the buck converter U4 is enabled; a resistor R4 (also called the fourth resistor) and a resistor R5 (also called the fifth resistor) are connected in parallel between the feedback terminal FB and the output terminal SW, and are grounded through a resistor R6 (or the sixth resistor). The resistor R5 is connected in series with the switch circuit S3 of the regulating sub-circuit 221. When the switch circuit S3 is turned on, the resistor R5 and the resistor R4 are connected in parallel to the feedback terminal FB and the output terminal SW of the buck converter U4; when the switch circuit S3 is turned off, the resistor R4 is connected to the feedback terminal FB and the output terminal SW of the buck converter U4. The buck converter U4 can stably reduce a relatively high input voltage to a relatively low output voltage by pulse width modulation (PWM).

In this way, the output voltage is adjusted by the feedback mechanism in combination with the above adjustment sub-circuit 221. As shown in FIG3, resistors R4 and R6 are connected in series to the output terminal SW of the buck converter U4, and the output voltage is adjusted by the voltage divider mechanism. As described above, resistor R5 is connected in parallel with resistor R4, and the dual voltage comparator U3 controls the switch circuit S3, thereby controlling whether the branch where the resistor R5 connected in series is located is turned on. When the switch circuit S3 is turned off, the equivalent voltage-dividing resistor above is the resistor R4; when the switch circuit S3 is turned on, the equivalent voltage-dividing resistor above is the parallel connection of the resistor R5 and the resistor R4, and the resistance value becomes relatively smaller; in this way, the output voltage of the buck converter U4 can be controlled by using the voltage-dividing mechanism, and the calculation formula is as follows:

V _out =V _ref (1+ ) (3)

Among them, V _out is the output voltage of the buck converter; V _ref is the reference voltage of the buck converter, which has a preset value, for example, in a chip of a buck converter, it is 0.6V; Ru is the upper resistance of the voltage divider branch, and Rd is the lower resistance of the voltage divider branch, wherein, when R5 is not connected, Ru is equal to R4, and when R5 is connected, Ru is equal to the parallel equivalent resistance of R4 and R5; Rd is R6.

Taking a lithium battery as an example, assuming that when the battery is powered normally, the expected output voltage is 1.5V; when the battery power is low, the expected output voltage is 1.0V. The full voltage output of the lithium battery is 4.2V, as shown in Figure 6. When the lithium battery starts to discharge from the full voltage, the output voltage of the battery cell is greater than or equal to 3.6V, the input terminal HTH of the dual voltage comparator U3 is triggered, that is, the upper edge voltage V _HI is triggered, and the output terminal outputs a high level (for example, 2.5V). The high level turns off the switch circuit S3, and the resistor R4 participates in the voltage division, while the resistor R5 does not participate in the voltage division. The output voltage of the buck converter U4 is calculated to be 1.5V by the voltage division formula (3). Then, the output voltage of the battery cell slowly drops to 3.1V, and the input terminal LTH of the dual voltage comparator U3 is triggered, that is, the lower edge voltage V _LO is triggered, and the output terminal outputs a low level. The low level turns on the switching circuit S3, and the resistors R4 and R5 participate in the voltage division. The output voltage of the buck converter is 1.0V calculated by the above voltage division formula (3).

In this way, a protection mechanism can be formed by monitoring the discharge voltage of the battery cell. When the battery cell voltage is low (for example, below 3.1V in the above scenario), the battery supply voltage can be reduced to 1.0V in advance, reducing the possibility of the battery discharge voltage suddenly dropping to 0V during over-discharge, giving users time to react in advance.

For example, when the user charges the battery, the voltage of the battery cell will rise. When it rises to a certain level, such as 3.6V, it will trigger the dual voltage comparator U3 to turn off the switch circuit S3. At this time, the resistor R5 will exit the voltage division, and the feedback resistance value of the buck converter U4 will return to the original R4. However, since it is currently in the charging state and the buck circuit is not turned on, the battery supply voltage will be adjusted back to 1.5V in the subsequent discharge process.

Furthermore, the buck converter U4 also includes an output status indicator terminal PG, also known as a good power supply (power good) indicator terminal, which is used to control the conduction and cutoff of the discharge circuit 220 through the switch circuit S4 (also known as the fourth switch circuit). Specifically, the switch circuit S4 is connected to the output status indicator terminal of the buck converter U4 and is located on the output path of the discharge circuit 220. When the output voltage of the buck converter U4 reaches 95% of the target value, the status indicator terminal PG will output a high level, so that the switch circuit S4 is turned on; when the output voltage of the buck converter U4 exceeds ±10% of the target value, the status indicator terminal PG will output a low level, so that the switch circuit S4 is disconnected, so as to provide stability of battery power supply.

In the above embodiment, when the battery is charged, the charger is connected, and the selection terminal Sel of the battery generates a selection voltage (for example, 1.8V-3.6V). The voltage detector U1 turns on the switch circuit S1 according to the selection voltage, and then turns on the charging circuit 210. The charging circuit 210 works to charge the battery cell (as shown in the charging path of the dotted arrow in FIG. 3 ). When the battery is discharged, the selection terminal Sel of the battery is unconnected or the voltage is low. The voltage detector U1 disconnects the switch circuit S1 according to the selection voltage, thereby shutting down the charging circuit 210. The charging circuit 210 does not work, and the discharge circuit 220 works. The discharge circuit 220 may have a front-end on/off mechanism. For example, when the charging circuit 210 is turned on, the buck converter U4 is enabled through the enable terminal EN of the buck converter U4. When the charging circuit 210 is disconnected, The discharge voltage of the battery cell enables the step-down converter U4; the discharge circuit 220 may also have a back-end on/off mechanism, for example, the voltage detector U2 turns on the switch circuit S2 during discharge, and turns off the switch circuit S2 during charging, so that double protection can be achieved and current backflow can be prevented; when the battery is discharged, the charging circuit 210 is turned off, the discharge circuit 220 is turned on, and the battery cell is discharged through the discharge circuit 220 (as shown in FIG. 3 , the discharge path indicated by the solid arrow).

Continuing with reference to FIG. 3 , in one embodiment of the present invention, the battery management circuit may further include a protection circuit for protecting the battery cells, for example, protection against over-discharge or over-charge, where the over-discharge lock voltage is, for example, 2.5V, and the over-discharge release voltage is, for example, 3.0V; the over-charge lock voltage is, for example, 4.2V, and the over-charge release voltage is, for example, 4.1V.

Each of the above switch circuits can be a transistor, such as a metal oxide semiconductor field effect (MOS) transistor. MOS transistors can be divided into two categories: N-channel and P-channel. The present invention can be selected according to needs. For example, the switch circuit can be a P-channel metal oxide semiconductor (PMOS) transistor or an N-channel metal oxide semiconductor (NMOS) transistor.

In conjunction with Figure 7, an embodiment of a battery management circuit is provided below. A person skilled in the art may derive other methods based on this, for example, replacement of transistors in a switch circuit, but the present invention is not limited thereto.

As shown in FIG7 , the switch circuit S1 includes an NMOS transistor Q1; correspondingly, the control circuit 230 includes: a voltage detector U1 and an NMOS transistor Q1. The input terminal V _in of the voltage detector U1 is connected to the selection terminal Sel, the output terminal V _OUT is connected to the gate of the NMOS transistor Q1, and the ground terminal GND is grounded; the source of the NMOS transistor Q1 is grounded, and the drain is connected to the charging circuit 210.

When the input voltage at the input terminal Vin of the voltage detector U1 is greater than the threshold voltage of the voltage detector U1, that is, when the voltage at the selection terminal Sel is detected to be greater than the threshold voltage of the voltage detector U1, the output terminal V _OUT of the voltage detector U1 outputs a high level to the gate of the NMOS transistor Q1, turning on the NMOS transistor Q1; correspondingly, when the input voltage at the input terminal _Vin of the voltage detector U1 is less than the threshold voltage of the voltage detector U1, that is, when the voltage at the selection terminal Sel is detected to be less than the threshold voltage of the voltage detector U1, the output terminal V OUT of the voltage detector U1 is turned off. _OUT outputs a low level to the gate of the NMOS transistor Q1, turning off the NMOS transistor Q1. The NMOS transistor Q1 is connected to the charging circuit 210, and further controls the charging circuit 210 to be turned on or off in the on state. For the scenario where the input voltage of the input terminal _Vin of the voltage detector U1 is equal to the threshold voltage, the output terminal _VOUT can output a high level or a low level.

Take the example of setting a select pole Sel on the battery, and the voltage of the select pole Sel during charging is between 1.8V and 3.6V, and the threshold voltage of the voltage detector U1 is 1.8V: during discharge, the select pole Sel is suspended, the voltage at the input end of the voltage detector U1 is less than the threshold voltage, the output is a low level, and the charging circuit 210 does not work; when the charger is connected for charging, when the voltage detector U1 detects that the voltage of the select pole Sel is greater than 1.8V, it provides a high level to the gate of the NMOS transistor Q1 to turn on the NMOS transistor Q1, and the charging circuit 210 works.

In one embodiment, the charging circuit 210 includes: a PMOS transistor Q5, a PMOS transistor Q6, a resistor R8, a capacitor C1, and a capacitor C2; the source of the PMOS transistor Q5, the source of the PMOS transistor Q6, the first end of the resistor R8, and the first end of the capacitor C1 are connected, the gate of the PMOS transistor Q5, the gate of the PMOS transistor Q6, the second end of the resistor R8, and the second end of the capacitor C1 are connected, and are connected to the drain of the NMOS transistor Q1, the drain of the PMOS transistor Q6, the first end of the capacitor C2, and the positive electrode of the battery are connected, the drain of the PMOS transistor Q5 is connected to the positive electrode of the battery cell, and the second end of the capacitor C2 is grounded.

During charging, NMOS transistor Q1 is turned on, and the gates of PMOS transistor Q5 and PMOS transistor Q6 receive a low level and are turned on at a low level; the charging circuit 210 works, and the charging signal charges the battery cell through the charging circuit 220. During discharge, NMOS transistor Q1 is turned off, and the gate and source voltages of PMOS transistor Q5 and PMOS transistor Q6 are equal, PMOS transistor Q5 and PMOS transistor Q6 are not turned on, and the charging circuit 210 is disconnected. In one embodiment, PMOS transistor Q5 and PMOS transistor Q6 are connected back to back to control the on and off of the charging circuit 210, further preventing the charging circuit 210 from being turned on during discharge.

In one embodiment, the discharge circuit 220 includes: a buck converter (or referred to as a voltage drop converter) U4, a capacitor C3, a capacitor C4, an inductor L1, a resistor R4, a resistor R6, and an NMOS transistor Q4.

The input terminal Vin of the buck converter U4 _is grounded through the capacitor C3 and connected to the positive electrode of the battery cell; the output terminal SW of the buck converter U4 is connected to the first end of the inductor L1, the second end of the inductor L1, the first end of the capacitor C4, the first end of the resistor R4, and the source of the NMOS transistor Q4; the feedback terminal FB of the buck converter U4 is connected to the second end of the resistor R4 and the first end of the resistor R6; the output status indication terminal PG of the buck converter U4 is connected to the gate of the NMOS transistor Q4, and the drain of the NMOS transistor Q4 serves as the output terminal of the discharge circuit 220 and can be connected to the positive electrode of the battery.

The above management circuit may also include a resistor R7 (also called the seventh resistor) and a diode D1. The resistor R7 and the diode D1 may be used as part of the discharge circuit 220, or as part of the charging circuit 210, or as an independent part. The first end of the resistor R7 is connected to the drain of the PMOS transistor Q5, and the second end is connected to the enable terminal EN of the buck converter U4; the positive electrode (or anode) of the diode D1 is connected to the second end of the resistor R7 and the enable terminal EN of the buck converter U4, and the negative electrode (or cathode) is connected to the gate of the PMOS transistor Q5, and is further connected to the drain of the NMOS transistor Q1.

During charging, the NMOS transistor Q1 is turned on, and the negative electrode of the diode D1 is grounded through the NMOS transistor Q1, so that the diode D1 is turned on, providing a low level to the enable terminal EN of the buck converter U4, and the buck converter U4 is disabled. During discharge, the diode D1 is cut off, and the positive electrode B+ of the battery cell provides a high level to the enable terminal of the buck converter U4 through the resistor R7; the buck converter U4 works, and the output terminal SW steps down the output voltage to the source of the NMOS transistor Q4 according to the feedback voltage signal provided by the first end of the resistor R4; when the output voltage is stable within the preset voltage range, the output status indication terminal PG of the buck converter U4 turns on the NMOS transistor Q4, so that the discharge circuit 220 is turned on.

In this embodiment, when the charging circuit 210 is turned on, the discharge circuit 220 is turned on by the diode D1, so that the enable terminal EN of the buck converter U4 receives a low voltage to enable the buck converter U4, and the discharge circuit 220 is turned off; when the charging circuit 210 is turned off, the battery cell starts to discharge, the diode D1 is turned off because the NMOS transistor Q1 is turned off, and the enable terminal EN of the buck converter U4 receives the enable signal provided by the battery cell through the resistor R7 and starts to work; the buck converter U4 is turned on according to the input terminal V The input voltage signal received by _in and the feedback voltage signal received by the feedback terminal FB are stepped down and output through the output terminal SW; when the output voltage is within the preset voltage range, the output status indication terminal PG of the buck converter U4 provides a gate voltage to the NMOS transistor Q4 to turn on the NMOS transistor Q4 and turn on the discharge circuit 220. When the output voltage is outside the preset voltage range, the NMOS transistor Q4 is turned off, so that when the output voltage does not meet the expectations, the discharge circuit 220 is disconnected.

Furthermore, the discharge circuit 220 also includes an adjustment sub-circuit 221; the adjustment sub-circuit 221 is the same as described above, including a dual voltage comparator U3 and a switch circuit S3, wherein the switch circuit S3 includes a PMOS transistor Q3; and the output terminal V _OUT of the dual voltage comparator U3 is connected to the gate of the PMOS transistor Q3 and the first end of the resistor R9, and the second end of the resistor R9 is connected to the output terminal of the discharge circuit 220, that is, the output terminal V _OUT of the dual voltage comparator U3 is connected to the first end of the resistor R5, the first end of the resistor R4 and the second end of the inductor L1 through the resistor R9.

When the output terminal V _OUT of the dual voltage comparator U3 outputs a high level, the PMOS transistor Q3 is turned off, R4 participates in the voltage division, and the buck converter U4 performs the first buck output. When the output terminal V _OUT of the dual voltage comparator U3 outputs a low level, the PMOS transistor Q3 is turned on, and the resistor R5 is connected in parallel with the resistor R4 to divide the voltage together, so that the resistor R6 obtains a larger divided voltage, and the voltage value of the feedback signal received by the feedback terminal FB of the buck converter U4 is increased; according to the feedback mechanism of the buck converter U4, the feedback terminal FB of the buck converter U4 changes the voltage output by the output terminal SW to perform a second buck output. As described in the above embodiment, the second buck output has a smaller voltage value.

In one embodiment, the back end of the discharge circuit 220 is also controlled to be turned on and off. For example, the control circuit 230 further includes a voltage detector U2 and a second switch circuit S2, wherein the second switch circuit S2 includes a PMOS transistor Q2; the input terminal Vin of the voltage detector U2, the source of the PMOS transistor Q2 and the positive electrode of the battery are connected, the output terminal V _OUT of the voltage detector U2 is connected to the gate of the PMOS transistor Q2, and the drain of the PMOS transistor Q2 is connected to the output terminal of the discharge circuit 220.

During discharge, the threshold voltage of the voltage detector U2 (e.g., 1.8V) is greater than the maximum output voltage of the battery (e.g., 1.5V). During discharge, the voltage at the input terminal _Vin of the voltage detector U2 is less than the threshold voltage of the voltage detector U2. The output terminal _VOUT of the voltage detector U2 outputs a low level to the gate of the PMOS transistor Q2, turning on the PMOS transistor Q2. The output terminal of the discharge circuit 220 provides a supply voltage to the positive electrode of the battery through the PMOS transistor Q2. When charging, the positive pole of the battery is connected to the charger. When the charging voltage (e.g., 4.2V) provided by the charger is greater than the threshold voltage of the voltage detector U2, the output terminal V _OUT of the voltage detector U2 outputs a high level to the gate of the PMOS transistor Q2, disconnecting the PMOS transistor Q2 to prevent the discharge circuit 220 from reversely conducting when the positive pole is connected to an over-high voltage power source, causing damage to the buck converter U4.

In one embodiment of the present invention, the protection circuit 240 includes a resistor R10, a capacitor C5, a cell protector U5, and a resistor R11; the first end of the resistor R10 is connected to the positive electrode B+ of the cell, the second end of the resistor R10 is connected to the positive input terminal VDD of the cell protector U5, and is connected to the first end of the capacitor C5; the second end of the capacitor C5 is connected to the negative electrode B- of the cell; the negative input terminal of the cell protector U5 is VDD. VSS and the first source terminal S1 are connected to the negative electrode B- of the battery cell, the second source terminal S2 of the battery cell protector U5 is connected to the negative electrode V- of the battery, and the negative input terminal VM of the charger of the battery cell protector U5 is connected to the second source terminal S2 through the resistor R11; the first source terminal S1 is the source of the discharge MOS tube, which is used to connect the negative electrode of the battery cell, and the second source terminal S2 is the source of the charging MOS tube, which is used to connect the negative input during charging.

The protection circuit 240 provides overcharge or over-discharge protection to the battery cell during the charging and discharging process of the battery cell.

In summary, the above embodiments introduce a selection terminal and a control circuit into the battery, and the control circuit uses the voltage of the selection terminal to control the state of the charging circuit or the discharging circuit, thereby turning on the charging circuit or the discharging circuit, thereby achieving battery charging and discharging management with lower complexity and reducing the cost of the battery.

It should be noted that the above embodiments can be freely combined as needed. The above are only some embodiments of the present invention. For ordinary technicians in this technical field, they can make some improvements and modifications without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention.

110: Housing 111: First electrode 112: Selector 120: Cell 121: Positive electrode of cell 130: Circuit board 200: Management circuit 210: Charging circuit 220: Discharging circuit 221: Adjustment subcircuit 230: Control circuit 240: Protection circuit 400: Dual voltage comparator

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments are briefly introduced below.

FIG1 is a structural diagram of a battery provided by an embodiment of the present invention;

FIG2 is a schematic diagram of a battery management circuit provided by an embodiment of the present invention;

FIG3 is a circuit diagram of a battery management circuit provided by an embodiment of the present invention;

FIG4 is a schematic diagram of a chip of a dual voltage comparator provided by an embodiment of the present invention;

FIG5 is a schematic diagram of input and output curves of the dual voltage comparator shown in FIG4;

FIG6 is a schematic diagram of the working process of a regulating sub-circuit of a discharge circuit provided by an embodiment of the present invention;

FIG. 7 is a circuit diagram of another battery management circuit provided by an embodiment of the present invention.

200: Management circuit

210: Charging circuit

220: Discharge circuit

230: Control circuit

Claims (10)

A battery management circuit includes: A charging circuit, one end of which is connected to the charging end of the battery to receive a charging signal, and the other end is connected to the positive electrode of the battery cell to provide a charging voltage to the battery cell; A discharging circuit, one end of which is connected to the positive electrode of the battery cell to receive a discharging signal, and the other end is connected to the power supply end of the battery to provide a power supply voltage; A control circuit, which is connected to the selection end of the battery and controls the states of the charging circuit and the discharging circuit according to the voltage of the selection end. The battery management circuit as described in claim 1, the control circuit comprises: A first voltage detector, the input end of the first voltage detector is connected to the selection end of the battery, and when the voltage at the selection end is greater than or equal to the threshold voltage of the first voltage detector, the output end of the first voltage detector outputs a first voltage; A first switch circuit, connected to the output end of the first voltage detector, when the output end of the first voltage detector outputs the first voltage, the first switch circuit is turned on, wherein the first switch circuit is connected to the charging circuit, and when the first switch circuit is turned on, the charging circuit is turned on. In the battery management circuit as described in claim 2, the threshold voltage of the first voltage detector is greater than the maximum supply voltage of the battery. The battery management circuit as described in claim 2 or 3, the control circuit further includes: A second voltage detector, the input end of the second voltage detector is connected to the charging end of the battery, and when the voltage at the charging end is greater than or equal to the threshold voltage of the second voltage detector, the output end of the second voltage detector outputs a second voltage; A second switch circuit, connected to the output end of the second voltage detector, when the output end of the second voltage detector outputs the second voltage, the second switch circuit is turned on, wherein the second switch circuit is connected to the discharge circuit), when the second switch circuit is turned on, the discharge circuit is turned on. The battery management circuit as described in claim 1 further includes: A negative temperature coefficient thermistor, one end of which is connected to the selected end of the battery and the other end is grounded. The battery management circuit as described in claim 1, the discharge circuit comprises: An adjusting subcircuit for adjusting the output voltage of the discharge circuit, wherein when the discharge signal of the battery cell is in a first range, the adjusting subcircuit adjusts the discharge circuit to output the supply voltage with a first value, and when the discharge signal of the battery cell is in a second range, the adjusting subcircuit adjusts the discharge circuit to output the supply voltage with a second value, and the first value is less than the second value. The battery management circuit as described in claim 6, the regulating subcircuit includes: A dual voltage comparator, including a first input terminal, a second input terminal, a third input terminal and an output terminal, wherein: The first input terminal is connected to the positive electrode of the battery cell; The second input terminal is connected to the positive electrode of the battery cell through a first resistor; The third input terminal is connected to the positive electrode of the battery cell through the first resistor and the second resistor, and is grounded through a third resistor; A third switch circuit is connected to the output terminal of the dual voltage comparator, and is turned on or off under the control of the output voltage of the output terminal, wherein when the third switch circuit is turned on, the discharge circuit outputs the supply voltage having the first value, and when the third switch circuit is turned off, the discharge circuit outputs the supply voltage having the second value. The battery management circuit as described in claim 7, the discharge circuit further includes: A buck converter, including an input terminal, an enable terminal, a feedback terminal, and an output terminal, wherein: The input terminal is connected to the positive electrode of the battery cell; The enable terminal disables the buck converter when the charging circuit is turned on, and enables the buck converter when the discharge circuit is turned on; A fourth resistor and a fifth resistor are connected in parallel between the feedback terminal and the output terminal, and are grounded through a sixth resistor, and the fifth resistor is connected in series with the third switch circuit. In the battery management circuit as described in claim 8, the enable terminal is connected to the control circuit through a diode and is connected to the positive electrode of the battery cell through a seventh resistor. As described in claim 8, the battery management circuit, the buck converter further includes an output status indication terminal, and the discharge circuit further includes: A fourth switch circuit, located on the output path of the discharge circuit, connected to the output status indication terminal of the buck converter.