A battery protection chip and system for positive terminal charging and discharging

Abstract

The invention relates to a positive terminal charging and discharging battery protection chip and system. The battery protection chip comprises a driving circuit, the driving circuit comprises a charging control branch, an overcharge protection output terminal of the charging control branch is used to connect a charging switch tube on a positive terminal charging circuit of a battery, the charging control branch comprises a pull-up unit and a pull-down unit, the pull-up unit is connected to a charging voltage, and pulls up the overcharge protection output terminal by acquiring a battery voltage and a charging voltage, the pull-down unit is grounded, and pulls down the overcharge protection output terminal by acquiring a battery voltage and a reference voltage, when the battery voltage is less than the sum of the reference voltage and a start-up voltage of a MOS tube, and the charging voltage is greater than the battery voltage, the pull-down of the pull-down unit is greater than the pull-up of the pull-up unit, so that the overcharge protection output terminal is at a low level, prompting the charging switch tube to be turned off, thereby avoiding battery damage caused by battery charging when the battery voltage is relatively low, so as to protect the battery and increase the battery life.

Description

Technical Field

[0001] The present invention is applicable to the technical field of battery protection, and in particular relates to a battery protection chip and system for positive terminal charging and discharging. Background Art

[0002] At present, the battery protection system uses a battery protection chip to control the battery charging and discharging circuit, so as to cut off the charging or discharging when the battery charging and discharging process encounters adverse conditions such as overcharging or over-discharging. Figure 1 As shown, it is a structural block diagram of an existing battery protection system, which includes a battery protection chip 1, a filter resistor R1, a filter capacitor C1, switch tubes M1 and M2 for controlling charge and discharge, and a resistor R2 for improving the electrostatic protection capability of VM voltage detection on the charge and discharge circuit. Among them, the battery protection chip 1 includes a charge pump, a detection circuit, a logic control circuit and a drive circuit. The charge is responsible for pumping the battery voltage VDD to a voltage higher than the battery voltage (such as 2*VDD voltage) to power the drive circuit so that it can turn on the charge and discharge control switch tubes M1 and M2. The detection circuit is used to monitor the size of the system charge and discharge current by detecting the voltage difference between P+ and B+. When the charge and discharge current is too large, the logic control circuit is used to implement charge and discharge protection for the system. The logic control circuit is responsible for receiving the output of the detection circuit and controlling the output of the drive circuit through the signal. The voltage of the drive circuit comes from the charge pump. The output of the logic control circuit is received to control the output of CO and DO to implement charge and discharge protection for the system. Figure 2 As shown, it is a schematic diagram of the structure of an existing driving circuit. CO and DO of the driving circuit are both CMOS outputs, and the charge pump output VCP voltage is used as the power supply. When the logic control circuit outputs ODP at a low level, DO is at a high level, and the DO tube M1 is controlled to be turned on. When the logic control circuit outputs ODP at a high level, DO is at a low level, and the DO tube M1 is controlled to be turned off. When the logic control circuit outputs OCP at a low level, CO is at a high level, and the CO tube M2 is controlled to be turned on. When the logic control circuit outputs OCP at a high level, CO is at a low level, and the CO tube M2 is controlled to be turned off. Since there are certain safety hazards in charging the battery when the battery voltage is low, the low-voltage charging prohibition method can avoid charging the battery. Based on the above structure, when the battery voltage is 0V, the charge pump will not work at this time, and the state of DO and CO cannot be guaranteed. At this time, if a charger is inserted, it may be possible to charge, which may cause battery damage and safety hazards, and reduce the service life of the battery. Therefore, how to ensure that the battery enters the charging prohibition state when the battery voltage is low to ensure the safety of use has become an urgent problem to be solved. Summary of the invention

[0003] In order to overcome the problem of how to ensure that the battery enters a charging-prohibited state when the battery voltage is low to ensure the safety of use, the present invention provides a battery protection chip and system for positive terminal charging and discharging.

[0004] In a first aspect, the present invention provides a battery protection chip for positive terminal charging and discharging.

[0005] The battery protection chip comprises a driving circuit, the driving circuit comprises a charging control branch, and the overcharge protection output end of the charging control branch is used to connect a charging switch tube arranged on the positive end charging circuit of the battery;

[0006] The charging control branch includes a pull-up unit and a pull-down unit;

[0007] The pull-up unit includes a first PMOS tube and a first current limiting element, the source of the first PMOS tube is used to connect the positive end charging circuit to obtain the charging voltage of the positive end charging circuit, the gate of the first PMOS tube is used to connect the voltage detection circuit of the battery to obtain the battery voltage of the battery, and the drain of the first PMOS tube is connected to the overcharge protection output terminal through the first current limiting element;

[0008] The pull-down unit includes a second PMOS tube, a first NMOS tube, and a second NMOS tube, wherein the source of the second PMOS tube is used to connect to the voltage detection circuit, and the gate of the second PMOS tube is connected to the reference voltage; the gate of the first NMOS tube is connected to the drain of the second PMOS tube, and the drain of the first NMOS tube is used to connect to the positive end charging circuit; the gate of the second NMOS tube is connected to the drain of the first NMOS tube, and the drain of the second NMOS tube is connected to the overshoot protection output terminal; the drain of the second PMOS tube, the source of the first NMOS tube, and the source of the second NMOS tube are all grounded;

[0009] When the battery voltage is less than the sum of the reference voltage and the turn-on voltage of the second PMOS tube, and the charging voltage is greater than the battery voltage, the pull-down of the second NMOS tube is greater than the pull-up of the first PMOS tube, so that the overcharge protection output terminal is at a low level.

[0010] In one embodiment, the pull-up unit further includes an anti-backflow element, the drain of the first PMOS tube is connected to the input end of the anti-backflow element through the first current limiting element, and the output end of the anti-backflow element is connected to the overcharge protection output end;

[0011] The anti-backflow element is a third PMOS tube or a diode. If the anti-backflow element is the third PMOS tube, the drain of the third PMOS tube is connected to the first current limiting element, and the source and gate of the third PMOS tube are both connected to the overcharge protection output end; or if the anti-backflow element is the diode, the anode of the diode is connected to the first current limiting element, and the cathode of the diode is connected to the overcharge protection output end.

[0012] In one embodiment, the pull-down unit further includes a second current limiting element, and the drain of the second PMOS tube is grounded through the second current limiting element;

[0013] The second current limiting element is a third NMOS tube or a first resistor. If the second current limiting element is the third NMOS tube, the drain of the second PMOS tube is connected to the drain of the third NMOS tube, and the source and gate of the third NMOS tube are both grounded; or if the second current limiting element is the first resistor, the drain of the second PMOS tube is grounded through the first resistor.

[0014] In one embodiment, the pull-down unit further includes a third current limiting element, and the drain of the first NMOS tube is used to connect to the positive terminal charging circuit through the third current limiting element;

[0015] The third current limiting element is a fourth NMOS tube or a second resistor. If the third current limiting element is the fourth NMOS tube, the drain of the first NMOS tube is connected to the source and gate of the fourth NMOS tube, and the drain of the fourth NMOS tube is used to connect to the positive end charging circuit; or if the third current limiting element is the second resistor, the drain of the first NMOS tube is used to connect to the positive end charging circuit through the first resistor.

[0016] In one embodiment, the charging control branch further includes a first CMOS circuit, the output of the first CMOS circuit is the overcharge protection output terminal, and the input of the first CMOS circuit is used to connect to the logic control circuit of the battery;

[0017] The driving circuit also includes a discharge control branch, which includes a second CMOS circuit, an input of which is used to connect to the logic control circuit, and an output of which is an over-discharge protection output terminal, which is used to connect to a discharge switch tube on a positive end discharge circuit of the battery.

[0018] In a second aspect, the present invention provides a positive end charging and discharging battery protection system, the battery protection system comprising a battery protection chip and a charging switch tube, the charging switch tube being used to be arranged on the positive end charging circuit of the battery;

[0019] The battery protection chip includes a drive circuit, the drive circuit includes a charging control branch, and the overcharge protection output end of the charging control branch is connected to the charging switch tube;

[0020] The charging control branch includes a pull-up unit and a pull-down unit;

[0021] The pull-up unit includes a first PMOS tube and a first current limiting element, the source of the first PMOS tube is used to connect the positive end charging circuit to obtain the charging voltage of the positive end charging circuit, the gate of the first PMOS tube is used to connect the voltage detection circuit of the battery to obtain the battery voltage of the battery, and the drain of the first PMOS tube is connected to the overcharge protection output terminal through the first current limiting element;

[0022] The pull-down unit includes a second PMOS tube, a first NMOS tube, and a second NMOS tube, wherein the source of the second PMOS tube is used to connect to the voltage detection circuit, and the gate of the second PMOS tube is connected to the reference voltage; the gate of the first NMOS tube is connected to the drain of the second PMOS tube, and the drain of the first NMOS tube is used to connect to the positive end charging circuit; the gate of the second NMOS tube is connected to the drain of the first NMOS tube, and the drain of the second NMOS tube is connected to the overshoot protection output terminal; the drain of the second PMOS tube, the source of the first NMOS tube, and the source of the second NMOS tube are all grounded;

[0023] When the battery voltage is less than the sum of the reference voltage and the turn-on voltage of the second PMOS tube, and the charging voltage is greater than the battery voltage, the pull-down of the second NMOS tube is greater than the pull-up of the first PMOS tube, so that the overcharge protection output terminal is at a low level.

[0024] In one embodiment, the pull-up unit further includes an anti-backflow element, the drain of the first PMOS tube is connected to the input end of the anti-backflow element through the first current limiting element, and the output end of the anti-backflow element is connected to the overcharge protection output end;

[0025] The anti-backflow element is a third PMOS tube or a diode. If the anti-backflow element is the third PMOS tube, the drain of the third PMOS tube is connected to the first current limiting element, and the source and gate of the third PMOS tube are both connected to the overcharge protection output end; or if the anti-backflow element is the diode, the anode of the diode is connected to the first current limiting element, and the cathode of the diode is connected to the overcharge protection output end.

[0026] In one embodiment, the pull-down unit further includes a second current limiting element, and the drain of the second PMOS tube is grounded through the second current limiting element;

[0027] The second current limiting element is a third NMOS tube or a first resistor. If the second current limiting element is the third NMOS tube, the drain of the second PMOS tube is connected to the drain of the third NMOS tube, and the source and gate of the third NMOS tube are both grounded; or if the second current limiting element is the first resistor, the drain of the second PMOS tube is grounded through the first resistor.

[0028] In one embodiment, the pull-down unit further includes a third current limiting element, and the drain of the first NMOS tube is used to connect to the positive terminal charging circuit through the third current limiting element;

[0029] The third current limiting element is a fourth NMOS tube or a second resistor. If the third current limiting element is the fourth NMOS tube, the drain of the first NMOS tube is connected to the source and gate of the fourth NMOS tube, and the drain of the fourth NMOS tube is used to connect to the positive end charging circuit; or if the third current limiting element is the second resistor, the drain of the first NMOS tube is used to connect to the positive end charging circuit through the first resistor.

[0030] In one embodiment, the charging control branch further includes a first CMOS circuit, the output of the first CMOS circuit is the overcharge protection output terminal, and the input of the first CMOS circuit is used to connect to the logic control circuit of the battery;

[0031] The driving circuit also includes a discharge control branch, which includes a second CMOS circuit, an input of which is used to connect to the logic control circuit, and an output of which is an over-discharge protection output terminal, which is used to connect to a discharge switch tube on a positive end discharge circuit of the battery.

[0032] Compared with the prior art, the embodiments of the present invention have the following beneficial effects: the driving circuit of the present invention includes a charging control branch, the overcharge protection output end of the charging control branch is used to connect the charging switch tube on the positive charging circuit, the charging control branch includes a pull-up unit and a pull-down unit, the pull-up unit includes a first PMOS tube and a first current limiting element, the source of the first PMOS tube is used to connect the positive charging circuit to obtain the charging voltage of the positive charging circuit, the gate of the first PMOS tube is used to connect the voltage detection circuit of the battery to obtain the battery voltage of the battery, the drain of the first PMOS tube is connected to the overcharge protection output end through the first current limiting element, the pull-down unit includes a second PMOS tube, a first NMOS tube and a second NMOS tube, the source of the second PMOS tube is used to connect the voltage detection circuit, and the gate of the first PMOS tube is used to connect the voltage detection circuit of the battery to obtain the battery voltage of the battery, the drain of the first PMOS tube is connected to the overcharge protection output end through the first current limiting element, the pull-down unit includes a second PMOS tube, a first NMOS tube and a second NMOS tube, the source of the second PMOS tube is used to connect the voltage detection circuit, and the gate of the first PMOS tube is used to connect the voltage detection circuit of the battery. The gate of the MOS tube is connected to the reference voltage; the gate of the first NMOS tube is connected to the drain of the second PMOS tube, the drain of the first NMOS tube is used to connect to the positive end charging circuit, the gate of the second NMOS tube is connected to the drain of the first NMOS tube, the drain of the second NMOS tube is connected to the overshoot protection output terminal, the drain of the second PMOS tube, the source of the first NMOS tube and the source of the second NMOS tube are all grounded, when the battery voltage is less than the sum of the reference voltage and the opening voltage of the second PMOS tube, and the charging voltage is greater than the battery voltage, the pull-down of the second NMOS tube is greater than the pull-up of the first PMOS tube, so that the overcharge protection output terminal is low level, prompting the charging switch tube to turn off, thereby avoiding battery damage caused by battery charging when the battery voltage is small, so as to protect the battery and increase the battery life. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0034] Figure 1 It is a structural block diagram of a battery protection system in the prior art;

[0035] Figure 2 It is a structural schematic diagram of a driving circuit of the prior art;

[0036] Figure 3 It is a structural schematic diagram of a positive terminal charging and discharging battery protection chip provided by one embodiment of the present invention;

[0037] Figure 4 It is a structural schematic diagram of a positive terminal charging and discharging battery protection chip provided by one embodiment of the present invention;

[0038] Figure 5It is a structural schematic diagram of a positive terminal charging and discharging battery protection chip provided by one embodiment of the present invention;

[0039] Figure 6 It is a structural schematic diagram of a positive terminal charging and discharging battery protection chip provided by one embodiment of the present invention;

[0040] Figure 7 It is a structural block diagram of a positive terminal charging and discharging battery protection system provided by one embodiment of the present invention;

[0041] Among them, 1. battery protection chip; 30. pull-up unit; 31. pull-down unit; 301. first PMOS tube; 302. first current limiting element; 303. anti-backflow element; 311. second PMOS tube; 312. first NMOS tube; 313. second NMOS tube; 314. second current limiting element; 315. third current limiting element; 3141. third NMOS tube; 3142. first resistor; 3151. fourth NMOS tube; 3152. second resistor; 3021. third resistor; 3031. third PMOS tube; 3032. diode; 51. first CMOS circuit; 52. second CMOS circuit; 70. battery protection system for positive terminal charging and discharging; 71. battery. DETAILED DESCRIPTION

[0042] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0043] In the description of the present invention, it should be understood that the terms "lateral", "vertical", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0044] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0045] See also Figure 3 , is a structural schematic diagram of a positive-end charging and discharging battery protection chip provided by an embodiment of the present invention. The above-mentioned driving circuit includes a charging control branch. The overcharge protection output terminal (CO) of the charging control branch is used to connect the charging switch tube on the positive-end charging circuit. When the charging switch tube is turned on, the positive-end charging circuit is turned on, and the battery can be charged. When the charging switch tube is turned off, the positive-end charging circuit is disconnected, and the battery cannot be charged.

[0046] The charging control branch includes a pull-up unit 30 and a pull-down unit 31. The pull-up unit 30 includes a first PMOS tube 301 and a first current limiting element 302. The source of the first PMOS tube 301 is used to connect to the positive end charging circuit to obtain the charging voltage VM of the positive end charging circuit. The gate of the first PMOS tube 301 is used to connect to the voltage detection circuit of the battery to obtain the battery voltage VDD of the battery. The drain of the first PMOS tube 301 is connected to CO through the first current limiting element. The pull-down unit 31 includes a second PMOS tube 311, a first NMOS tube 312 and a second NMOS tube 313. The source of the second PMOS tube 311 is connected to the battery voltage detection circuit to obtain the battery voltage VDD of the battery. The gate of the second PMOS tube 311 is connected to the reference voltage; the gate of the first NMOS tube 312 is connected to the drain of the second PMOS tube 311, and the drain of the first NMOS tube 312 is used to connect to the positive charging circuit, so as to obtain the charging voltage VM of the positive charging circuit; the gate of the second NMOS tube 313 is connected to the drain of the first NMOS tube 312, and the drain of the second NMOS tube 313 is connected to the overshoot protection output terminal CO; the drain of the second PMOS tube 311, the source of the first NMOS tube 313 and the source of the second NMOS tube 311 are all grounded.

[0047] When the charger is inserted, the charging voltage VM will be higher than the battery voltage VDD. When the battery voltage VDD is less than the sum of the reference voltage VREF and the turn-on voltage of the second PMOS tube 311, and the charging voltage VM is greater than the battery voltage VDD, for the pull-down unit 31, the second PMOS tube 311 is turned off, and the gate voltage of the first NMOS tube 312 is 0, so that the first NMOS tube 312 is turned off, so that the gate voltage of the second NMOS tube 313 is the charging voltage VM, so that the second NMOS tube is turned on. Since the second NMOS tube 313 is grounded, the overcharge CO is pulled down; for the pull-up unit 30, the first PMOS tube 301 is turned on, and the source of the first PMOS tube 301 is connected to the charging voltage VM, so that the overcharge protection output terminal CO is pulled up. Due to the existence of the first current limiting element 302, and the second NMOS tube 313 is directly grounded, therefore, the pull-down of the second NMOS tube 313 is greater than the pull-up of the first PMOS tube 301, so that the overcharge CO is a low level. After the battery voltage VDD recovers to be greater than the sum of the reference voltage VREF and the turn-on voltage of the second PMOS tube 311, the second PMOS tube 311 is turned on, and the gate voltage of the first NMOS tube 312 is the battery voltage VDD, so that the first NMOS tube 312 is turned on, so that the charging voltage VM is grounded, and the gate voltage of the second NMOS tube 313 is 0, so that the second NMOS tube is turned off, and the over CO is no longer pulled down, while the pull-up unit 30 still maintains a pull-up trend, so that the over CO is at a high level, the battery charging can be restored, and the 0V charging prohibition function is realized.

[0048] In one embodiment, if Figure 3 As shown, the pull-up unit 30 further includes an anti-backflow element 303 , the drain of the first PMOS tube 301 is connected to the input end of the anti-backflow element 303 through the first current limiting element 302 , and the output end of the anti-backflow element 303 is connected to CO.

[0049] In one embodiment, if Figure 4 As shown, the pull-down unit 31 further includes a second current limiting element 314, and the drain of the second PMOS tube 311 is grounded through the second current limiting element 314. In addition, the pull-down unit 31 further includes a third current limiting element 315, and the drain of the first NMOS tube 312 is used to connect to the positive terminal charging circuit through the third current limiting element 315, that is, to obtain the charging voltage VM.

[0050] See also Figure 5 and Figure 6 , in the above Figure 3 and Figure 4On the basis of, in one embodiment, the anti-backflow element 303 is a third PMOS tube 3031, the drain of the third PMOS tube 3031 is connected to the third resistor 3021, and the source and gate of the third PMOS tube 3031 are both connected to CO. The third resistor 3021 is the first current limiting element 302. The third PMOS tube 3031 is to prevent the CO voltage from backflowing to the charger through the first PMOS tube 301 during normal operation.

[0051] In one embodiment, the second current limiting element 314 is a third NMOS transistor 3141 , the drain of the second PMOS transistor 311 is connected to the drain of the third NMOS transistor 3141 , and the source and gate of the third NMOS transistor 3141 are both grounded.

[0052] In one embodiment, the third current limiting element 315 is a fourth NMOS tube 3151, the drain of the first NMOS tube 312 is connected to the source and gate of the fourth NMOS tube 3151, and the drain of the fourth NMOS tube 3151 is used to connect to the positive end charging circuit to obtain the charging voltage VM.

[0053] When the charger is inserted, the charging voltage VM will be higher than the battery voltage VDD. If the second current limiting element 314 is the third NMOS tube 3141, the third current limiting element 315 is the fourth NMOS tube 3151, and the backflow prevention element 303 is the third PMOS tube 3031, since the VDD voltage is close to 0V, the second PMOS tube 311 is turned off, and the third NMOS tube 3141 is an N-type power dissipation transistor. At this time, the voltage at the drain of the third NMOS tube 3141 is a low level, causing the first NMOS tube 312 to be turned off. The fourth NMOS tube 3151 is an N-type power dissipation transistor. At this time, the voltage at the drain of the first NMOS tube is the charging voltage VM, so that the second NMOS tube 313 is turned on. Due to the third resistor 3021, the pull-down of CO by the second NMOS tube 313 is stronger than VM on C. O is pulled up, so CO is a constant low level, thereby realizing the 0V charging prohibition function. When the battery voltage VDD rises to higher than VREF+VTH (VTH is the turn-on voltage of the second PMOS tube 311), the second PMOS tube 311 is turned on, and the third NMOS tube 3141 is an N-type power dissipation transistor. At this time, the voltage at the drain of the third NMOS tube 3141 is the VDD level, causing the first NMOS tube 312 to be turned on. The fourth NMOS tube 3151 is an N-type power dissipation transistor, so the voltage at the drain of the first NMOS tube 312 is a low level, making the second NMOS tube 313 turned off, and the pull-down of CO by the second NMOS tube 313 disappears. Since VM has a weak pull-up capability on CO through the first PMOS tube 301, CO is the VM voltage at this time, thereby realizing the charging function.

[0054] The above driving circuit can realize that when the battery voltage is lower than VREF+VTH, especially when the battery voltage is lower than 0V, the battery cannot be charged by inserting a charger, and when the battery voltage is higher than VREF+VTH, the battery can be charged again by inserting a charger.

[0055] In one embodiment, the anti-backflow element 303 is a diode 3032, the anode of the diode 3032 is connected to the third resistor 3021, and the cathode of the diode is connected to CO. The third resistor 3021 is also the first current limiting element 301. The diode 3032 is used to prevent the CO voltage from backflowing to the charger through the first PMOS tube 301 during normal operation.

[0056] In one implementation, the second current limiting element 314 is a first resistor 3142 , and the drain of the second PMOS transistor 311 is grounded through the first resistor 3142 .

[0057] In one embodiment, the third current limiting element 315 is a second resistor 3152 , and the drain of the first NMOS transistor 312 is connected to a positive charging circuit through the first resistor 3152 to obtain a charging voltage VM.

[0058] When the charger is inserted, the charging voltage VM will be higher than the battery voltage VDD. If the second current limiting element 314 is the first resistor 3142, the third current limiting element 315 is the second resistor 3152, and the backflow prevention element 303 is the diode 3032, since the VDD voltage is close to 0V, the second PMOS tube 311 is turned off, and the voltage at the drain of the second PMOS tube 311 is low, causing the first NMOS tube 312 to be turned off, and the voltage at the drain of the first NMOS tube is the charging voltage VM, so that the second NMOS tube 313 is turned on. Due to the third resistor 3021, the pull-down of CO by the second NMOS tube 313 is stronger than the pull-up of CO by VM, so With CO as a constant low level, the 0V charging prohibition function is realized. When the battery voltage VDD rises to a level higher than VREF+VTH (VTH is the turn-on voltage of the second PMOS tube 311), the second PMOS tube 311 is turned on, and the voltage at the drain of the second PMOS tube 311 is at the VDD level, causing the first NMOS tube 312 to be turned on. Therefore, the voltage at the drain of the first NMOS tube 312 is at a low level, so that the second NMOS tube 313 is turned off, and the pull-down of CO by the second NMOS tube 313 disappears. Since VM has a weak pull-up capability on CO through the first PMOS tube 301, CO is at the VM voltage at this time, thereby realizing the charging function.

[0059] The above driving circuit can realize that when the battery voltage is lower than VREF+VTH, especially when the battery voltage is lower than 0V, the battery cannot be charged by inserting a charger, and when the battery voltage is higher than VREF+VTH, the battery can be charged again by inserting a charger.

[0060] In one embodiment, the charging control branch further includes a first CMOS circuit 51, the output of the first CMOS circuit 51 is over CO, and the input of the first CMOS circuit 51 is used to connect to the logic control circuit of the battery to obtain the OCP control signal sent by the logic control circuit to realize the charging control, overcharging control, etc. of the battery.

[0061] In one embodiment, the driving circuit further includes a discharge control branch, which includes a second CMOS circuit 52. The output of the second CMOS circuit 52 is an over-discharge protection output terminal (DO), and DO is used to connect the discharge switch tube on the positive discharge circuit of the battery. When the discharge switch tube is turned on, the positive discharge circuit of the battery is turned on, and the battery can be discharged. When the discharge switch tube is turned off, the positive discharge circuit of the battery is disconnected, and the battery cannot be discharged. The input of the second CMOS circuit 52 is used to connect the logic control circuit to obtain the ODP control signal sent by the logic control circuit to realize the discharge control, over-discharge control, etc. of the battery. Figure 5 and Figure 6 The CMOS circuit is composed of a PMOS tube and an NMOS tube.

[0062] During normal operation, the logic control circuit outputs ODP and OCP are both low levels. After passing through the drive circuit, CO and DO are high levels, that is, normal charging and discharging of the battery; when over-discharge or discharge overcurrent occurs, ODP becomes high level, at this time DO is low level, and the discharge switch tube is controlled to be turned off to achieve discharge protection; when over-charging or charging overcurrent occurs, OCP becomes high level, at this time CO is low level, and the charging switch tube is controlled to be turned off to achieve charging protection.

[0063] When the battery voltage is 0V, the charge pump will not work, so the status of DO and CO cannot be guaranteed. If a charger is inserted at this time, charging may be possible, which will cause a safety hazard. The existing charging and discharging circuit is integrated, and the charging switch tube and the discharging switch tube are arranged front and back. Generally, the charging switch tube is closer to the battery than the discharging switch tube. Since the status of DO cannot prevent the charging current from flowing through the switch tube controlled by CO (the current can flow through the parasitic diode of the discharging switch tube), therefore, to ensure that charging is prohibited, CO must be at a low level.

[0064] See also Figure 7, which is a structural block diagram of a positive terminal charging and discharging battery protection system 70 provided by the present invention, wherein the battery protection system 70 includes a charge pump, an overcurrent protection circuit, a voltage detection circuit, a logic control circuit and a drive circuit. The charge pump is responsible for pumping the battery voltage VDD to a level higher than the battery voltage, which is used to power the drive circuit so that the drive circuit can turn on the charge and discharge switch tube. The overcurrent protection circuit detects the charge and discharge voltage. The voltage detection circuit implements battery overcharge and over-discharge protection by detecting the battery voltage. The logic control circuit is responsible for receiving the outputs of the voltage detection circuit and the overcurrent protection circuit, thereby controlling the output of the drive circuit. The voltage of the drive circuit comes from the charge pump, and the charging and discharging protection of the battery 71 is implemented by controlling the outputs of CO and DO by receiving the output of the logic control circuit.

[0065] The positive-end charging and discharging battery protection system 70 is used to protect the battery 71. The positive electrode of the charging and discharging circuit of the battery 71 is provided with a discharge switch tube M3, a charging switch tube M4, and an overcurrent protection resistor R6. In addition, the filter resistor R5 and the filter capacitor C2 are connected to the voltage detection circuit. The overcurrent protection circuit is used to detect the charging voltage and the discharging voltage. The system charging and discharging current is monitored according to the voltage difference of the overcurrent protection resistor R6 (i.e., the voltage difference between VM and VINI). When the charging and discharging current is too large, the charging and discharging protection of the system is realized through the logic control circuit. The discharge voltage detection is connected to the end of the overcurrent protection resistor R6 close to the battery 71 through the resistor R3. The charging voltage detection is connected to the end of the overcurrent protection resistor R6 away from the battery 71 through the resistor R4. The resistor R3 and the resistor R4 are respectively used to improve the electrostatic protection capability.

[0066] Under normal circumstances, the battery voltage is between the over-discharge voltage and the over-charge voltage, and the charge and discharge current value is within the over-current protection threshold. At this time, the logic control circuit controls the outputs CO and DO of the drive circuit to be high, and the battery 71 can be charged and discharged normally. When the voltage detection circuit detects that the battery voltage VDD is lower than the over-discharge voltage threshold, the output of the voltage detection circuit is reversed, and the logic control circuit controls the output DO of the drive circuit to be low and CO to be high, thereby prohibiting the battery 71 from being discharged. When the voltage detection circuit detects that the battery voltage VDD is higher than the over-charge voltage threshold, the output of the voltage detection circuit is reversed, and the logic control circuit controls The output CO of the drive circuit is at a low level and DO is at a high level, thereby prohibiting charging of the battery 71; when the overcurrent protection circuit detects that VINI is higher than VM by the discharge overcurrent threshold VDI, the output of the overcurrent protection circuit flips, and the logic control circuit controls the output DO of the drive circuit to be at a low level and CO to be at a high level, thereby prohibiting discharging of the battery 71; when the overcurrent protection circuit detects that VM is higher than VINI by the charging overcurrent threshold VCI, the output of the overcurrent protection circuit flips, and the logic control circuit controls the output CO of the drive circuit to be at a low level and DO to be at a high level, thereby prohibiting charging of the battery 71.

[0067] The overcurrent detection of the battery protection system of the present invention realizes charging and discharging protection of the system by detecting the voltage drop of the overcurrent protection resistor R6. Since the resistance of the overcurrent protection resistor R6 does not change with the voltage and temperature of the battery 71, the overcurrent value of the battery protection system using the present invention is very stable, which is beneficial to protecting the safety of the battery 71.

[0068] The driving circuit of the present invention also has a 0V charging prohibition function, see Figures 3 to 6 As shown, the above-mentioned driving circuit includes a charging control branch, and the CO of the charging control branch is connected to the charging switch tube M4. When the charging switch tube M4 is turned on, the positive charging circuit is turned on, and the battery 71 can be charged. When the charging switch tube M4 is turned off, the positive charging circuit is disconnected, and the battery 71 cannot be charged.

[0069] The charging control branch includes a pull-up unit 30 and a pull-down unit 31. The pull-up unit 30 includes a first PMOS tube 301 and a first current limiting element 302. The source of the first PMOS tube 301 is connected to the VM of the overcurrent protection circuit to obtain the charging voltage VM of the positive charging circuit. The gate of the first PMOS tube 301 is connected to the output of the voltage detection circuit to obtain the battery voltage VDD of the battery 71. The drain of the first PMOS tube 301 is connected to CO through the first current limiting element. The pull-down unit 31 includes a second PMOS tube 311, a first NMOS tube 312 and a second NMOS tube 313. The source of the second PMOS tube 311 is connected to the output of the voltage detection circuit to obtain the battery voltage VDD of the battery 71. The output of the voltage detection circuit is connected to obtain the battery voltage VDD of the battery 71, and the gate of the second PMOS tube 311 is connected to the reference voltage; the gate of the first NMOS tube 312 is connected to the drain of the second PMOS tube 311, and the drain of the first NMOS tube 312 is connected to the VM of the overcurrent protection circuit, so as to obtain the charging voltage VM of the positive charging circuit; the gate of the second NMOS tube 313 is connected to the drain of the first NMOS tube 312, and the drain of the second NMOS tube 313 is connected to the overshoot protection output terminal CO; the drain of the second PMOS tube 311, the source of the first NMOS tube 313 and the source of the second NMOS tube 311 are all grounded.

[0070] When the charger is inserted, the charging voltage VM will be higher than the battery voltage VDD. When the battery voltage VDD is less than the sum of the reference voltage VREF and the turn-on voltage of the second PMOS tube 311, and the charging voltage VM is greater than the battery voltage VDD, for the pull-down unit 31, the second PMOS tube 311 is turned off, and the gate voltage of the first NMOS tube 312 is 0, so that the first NMOS tube 312 is turned off, so that the gate voltage of the second NMOS tube 313 is the charging voltage VM, so that the second NMOS tube is turned on. Since the second NMOS tube 313 is grounded, the overcharge CO is pulled down; for the pull-up unit 30, the first PMOS tube 301 is turned on, and the source of the first PMOS tube 301 is connected to the charging voltage VM, so that the overcharge protection output terminal CO is pulled up. Due to the existence of the first current limiting element 302, and the second NMOS tube 313 is directly grounded, therefore, the pull-down of the second NMOS tube 313 is greater than the pull-up of the first PMOS tube 301, so that the overcharge CO is a low level. After the battery voltage VDD recovers to be greater than the sum of the reference voltage VREF and the turn-on voltage of the second PMOS tube 311, the second PMOS tube 311 is turned on, and the gate voltage of the first NMOS tube 312 is the battery voltage VDD, so that the first NMOS tube 312 is turned on, so that the charging voltage VM is grounded, and the gate voltage of the second NMOS tube 313 is 0, so that the second NMOS tube is turned off, and the pass CO is no longer pulled down, while the pull-up unit 30 still maintains a pull-up trend, therefore, the pass CO is at a high level, and the charging of the battery 71 can be restored.

[0071] In one embodiment, the pull-up unit 30 further includes an anti-backflow element 303 , the drain of the first PMOS tube 301 is connected to the input end of the anti-backflow element 303 through the first current limiting element 302 , and the output end of the anti-backflow element 303 is connected to CO.

[0072] In one embodiment, the pull-down unit 31 further includes a second current limiting element 314, and the drain of the second PMOS tube 311 is grounded through the second current limiting element 314. In addition, the pull-down unit 31 further includes a third current limiting element 315, and the drain of the first NMOS tube 312 is connected to the VM of the overcurrent protection circuit through the third current limiting element 315, that is, the charging voltage VM is obtained.

[0073] In one embodiment, the anti-backflow element 303 is a third PMOS tube 3031, the drain of the third PMOS tube 3031 is connected to the third resistor 3021, and the source and gate of the third PMOS tube 3031 are both connected to CO. The third resistor 3021 is the first current limiting element 302. The third PMOS tube 3031 is to prevent the CO voltage from backflowing to the charger through the first PMOS tube 301 during normal operation.

[0074] In one embodiment, the second current limiting element 314 is a third NMOS transistor 3141 , the drain of the second PMOS transistor 311 is connected to the drain of the third NMOS transistor 3141 , and the source and gate of the third NMOS transistor 3141 are both grounded.

[0075] In one embodiment, the third current limiting element 315 is a fourth NMOS tube 3151, the drain of the first NMOS tube 312 is connected to the source and gate of the fourth NMOS tube 3151, and the drain of the fourth NMOS tube 3151 is connected to the VM of the overcurrent protection circuit to obtain the charging voltage VM.

[0076] In one embodiment, the anti-backflow element 303 is a diode 3032, the anode of the diode 3032 is connected to the third resistor 3021, and the cathode of the diode is connected to CO. The third resistor 3021 is also the first current limiting element 301. The diode 3032 is used to prevent the CO voltage from backflowing to the charger through the first PMOS tube 301 during normal operation.

[0077] In one implementation, the second current limiting element 314 is a first resistor 3142 , and the drain of the second PMOS transistor 311 is grounded through the first resistor 3142 .

[0078] In one embodiment, the third current limiting element 315 is a second resistor 3152 , and the drain of the first NMOS transistor 312 is connected to VM of the overcurrent protection circuit through the first resistor 3152 to obtain the charging voltage VM.

[0079] In one embodiment, the charging control branch further includes a first CMOS circuit 51, the output of the first CMOS circuit 51 is over CO, and the input of the first CMOS circuit 51 is connected to the logic control circuit to obtain the OCP control signal sent by the logic control circuit to realize charging control, overcharging control, etc. of the battery 71.

[0080] In one embodiment, the driving circuit further includes a discharge control branch, which includes a second CMOS circuit 52, and the output of the second CMOS circuit 52 is DO, which is connected to the discharge switch tube M3. When the discharge switch tube M3 is turned on, the positive end discharge circuit of the battery is turned on, and the battery 71 can be discharged. When the discharge switch tube M3 is turned off, the positive end discharge circuit of the battery is disconnected, and the battery 71 cannot be discharged. The input of the second CMOS circuit 52 is connected to the logic control circuit to obtain the ODP control signal sent by the logic control circuit to realize the discharge control, over-discharge control, etc. of the battery 71.

[0081] The present invention does not limit the order of the above steps. The order of the above steps is related to the specific implementation process. The process implemented by the above steps is the same as the implementation process of each circuit in the battery protection chip for positive terminal charging and discharging, and will not be repeated here. When implementing the method, it can be packaged into a control program and installed in the memory of the corresponding processor. The processor processes the program to implement the above method.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A battery protection chip for positive terminal charging and discharging, characterized in that: The battery protection chip comprises a driving circuit, the driving circuit comprises a charging control branch, and the overcharge protection output end of the charging control branch is used to connect a charging switch tube arranged on the positive end charging circuit of the battery; The charging control branch includes a pull-up unit and a pull-down unit; The pull-up unit includes a first PMOS tube and a first current limiting element, the source of the first PMOS tube is used to connect the positive end charging circuit to obtain the charging voltage of the positive end charging circuit, the gate of the first PMOS tube is used to connect the voltage detection circuit of the battery to obtain the battery voltage of the battery, and the drain of the first PMOS tube is connected to the overcharge protection output terminal through the first current limiting element; The pull-down unit includes a second PMOS tube, a first NMOS tube and a second NMOS tube, the source of the second PMOS tube is used to connect to the voltage detection circuit, and the gate of the second PMOS tube is connected to the reference voltage; the gate of the first NMOS tube is connected to the drain of the second PMOS tube, and the drain of the first NMOS tube is used to connect to the positive end charging circuit; The gate of the second NMOS tube is connected to the drain of the first NMOS tube, and the drain of the second NMOS tube is connected to the overcharge protection output terminal; the drain of the second PMOS tube, the source of the first NMOS tube and the source of the second NMOS tube are all grounded; When the battery voltage is less than the sum of the reference voltage and the turn-on voltage of the second PMOS tube, and the charging voltage is greater than the battery voltage, the pull-down of the second NMOS tube is greater than the pull-up of the first PMOS tube, so that the overcharge protection output terminal is at a low level.

2. The battery protection chip according to claim 1, characterized in that: The pull-up unit further includes an anti-backflow element, the drain of the first PMOS tube is connected to the input end of the anti-backflow element through the first current limiting element, and the output end of the anti-backflow element is connected to the overcharge protection output end; The anti-backflow element is a third PMOS tube or a diode. If the anti-backflow element is the third PMOS tube, the drain of the third PMOS tube is connected to the first current limiting element, and the source and gate of the third PMOS tube are both connected to the overcharge protection output end; or if the anti-backflow element is the diode, the anode of the diode is connected to the first current limiting element, and the cathode of the diode is connected to the overcharge protection output end.

3. The battery protection chip according to claim 1, characterized in that: The pull-down unit further includes a second current limiting element, and the drain of the second PMOS tube is grounded through the second current limiting element; The second current limiting element is a third NMOS tube or a first resistor. If the second current limiting element is the third NMOS tube, the drain of the second PMOS tube is connected to the drain of the third NMOS tube, and the source and gate of the third NMOS tube are both grounded; or if the second current limiting element is the first resistor, the drain of the second PMOS tube is grounded through the first resistor.

4. The battery protection chip according to claim 1, characterized in that: The pull-down unit further includes a third current limiting element, and the drain of the first NMOS tube is used to connect to the positive end charging circuit through the third current limiting element; The third current limiting element is a fourth NMOS tube or a second resistor. If the third current limiting element is the fourth NMOS tube, the drain of the first NMOS tube is connected to the source and gate of the fourth NMOS tube, and the drain of the fourth NMOS tube is used to connect to the positive end charging circuit; or if the third current limiting element is the second resistor, the drain of the first NMOS tube is connected to the positive end charging circuit through the second resistor.

5. The battery protection chip according to claim 1, characterized in that: The charging control branch further includes a first CMOS circuit, the output of the first CMOS circuit is the overcharge protection output terminal, and the input of the first CMOS circuit is used to connect to the logic control circuit of the battery; The driving circuit also includes a discharge control branch, which includes a second CMOS circuit, an input of which is used to connect to the logic control circuit, and an output of which is an over-discharge protection output terminal, which is used to connect to a discharge switch tube on a positive end discharge circuit of the battery.

6. A positive terminal charging and discharging battery protection system, characterized in that: The battery protection system includes a battery protection chip and a charging switch tube, wherein the charging switch tube is used to be arranged on the positive charging circuit of the battery; The battery protection chip includes a drive circuit, the drive circuit includes a charging control branch, and the overcharge protection output end of the charging control branch is connected to the charging switch tube; The charging control branch includes a pull-up unit and a pull-down unit; The pull-up unit includes a first PMOS tube and a first current limiting element, the source of the first PMOS tube is used to connect to the positive end charging circuit to obtain the charging voltage of the positive end charging circuit, the gate of the first PMOS tube is used to connect to the voltage detection circuit of the battery to obtain the battery voltage of the battery, and the drain of the first PMOS tube is connected to the overcharge protection output terminal through the first current limiting element; The pull-down unit includes a second PMOS tube, a first NMOS tube and a second NMOS tube, the source of the second PMOS tube is used to connect to the voltage detection circuit, and the gate of the second PMOS tube is connected to the reference voltage; the gate of the first NMOS tube is connected to the drain of the second PMOS tube, and the drain of the first NMOS tube is used to connect to the positive end charging circuit; The gate of the second NMOS tube is connected to the drain of the first NMOS tube, and the drain of the second NMOS tube is connected to the overcharge protection output terminal; the drain of the second PMOS tube, the source of the first NMOS tube and the source of the second NMOS tube are all grounded; When the battery voltage is less than the sum of the reference voltage and the turn-on voltage of the second PMOS tube, and the charging voltage is greater than the battery voltage, the pull-down of the second NMOS tube is greater than the pull-up of the first PMOS tube, so that the overcharge protection output terminal is at a low level.

7. The battery protection system according to claim 6, characterized in that: The pull-up unit further includes an anti-backflow element, the drain of the first PMOS tube is connected to the input end of the anti-backflow element through the first current limiting element, and the output end of the anti-backflow element is connected to the overcharge protection output end; The anti-backflow element is a third PMOS tube or a diode. If the anti-backflow element is the third PMOS tube, the drain of the third PMOS tube is connected to the first current limiting element, and the source and gate of the third PMOS tube are both connected to the overcharge protection output end; or if the anti-backflow element is the diode, the anode of the diode is connected to the first current limiting element, and the cathode of the diode is connected to the overcharge protection output end.

8. The battery protection system according to claim 6, characterized in that: The pull-down unit further includes a second current limiting element, and the drain of the second PMOS tube is grounded through the second current limiting element; The second current limiting element is a third NMOS tube or a first resistor. If the second current limiting element is the third NMOS tube, the drain of the second PMOS tube is connected to the drain of the third NMOS tube, and the source and gate of the third NMOS tube are both grounded; or if the second current limiting element is the first resistor, the drain of the second PMOS tube is grounded through the first resistor.

9. The battery protection system according to claim 6, characterized in that: The pull-down unit further includes a third current limiting element, and the drain of the first NMOS tube is used to connect to the positive end charging circuit through the third current limiting element; The third current limiting element is a fourth NMOS tube or a second resistor. If the third current limiting element is the fourth NMOS tube, the drain of the first NMOS tube is connected to the source and gate of the fourth NMOS tube, and the drain of the fourth NMOS tube is used to connect to the positive end charging circuit; or if the third current limiting element is the second resistor, the drain of the first NMOS tube is connected to the positive end charging circuit through the second resistor.

10. The battery protection system according to claim 6, characterized in that: The charging control branch further includes a first CMOS circuit, the output of the first CMOS circuit is the overcharge protection output terminal, and the input of the first CMOS circuit is used to connect to the logic control circuit of the battery; The driving circuit also includes a discharge control branch, which includes a second CMOS circuit, an input of which is used to connect to the logic control circuit, and an output of which is an over-discharge protection output terminal, which is used to connect to a discharge switch tube on a positive end discharge circuit of the battery.

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