Battery charging drive circuit and battery protection chip

Abstract

The embodiment of the invention provides a battery charging driving circuit and a battery protection chip, and relates to the technical field of battery protection, and the battery charging driving circuit comprises a zero-volt charging forbidding driving switch which is switched on when a battery is in a zero-volt state and is connected with a charger; the first voltage division circuit is connected in series with the zero-volt charging forbidding driving switch and then is connected between the power supply end of the battery protection chip and the charging negative voltage access end; the drain electrode of the pull-down MOS tube is used for being connected with the charging control end of the battery protection chip, and the grid electrode and the source electrode of the pull-down MOS tube are connected through a second resistor in the first voltage division circuit. The pull-down MOS tube can be realized by selecting a common low-voltage MOS tube, and compared with the prior art, one more choice is provided. When a low-voltage MOS tube is used as a pull-down device of CO voltage, compared with an existing pull-down device using a thick gate oxide MOS tube, the area can be reduced, mask layers can be reduced, and then the chip cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of battery protection, and in particular to a battery charging drive circuit and a battery protection chip. Background Art

[0002] At present, in order to ensure the safe application of batteries, batteries are usually equipped with protection chips to monitor the battery status. The chip controls charging and discharging by monitoring the battery voltage between the power supply terminal (VDD) and the battery negative input terminal (VSS) and the voltage between the charging negative voltage access terminal (VM) and VSS.

[0003] Among them, a battery protection chip charging application such as Figure 1 As shown, the battery is connected to the charger through the charge and discharge switch. The chip controls the charging control terminal (CO) voltage relative to the VM voltage to control the on and off of the switch tube M2. The diode in the switch tube M1 controlled by the discharge control terminal (DO) forms a charging loop, thereby controlling whether the battery can be charged.

[0004] In some application scenarios, in order to further improve the safety of the battery during use, a zero-volt charging prohibition function is designed for the existing battery protection chip. By controlling the CO voltage of the battery protection chip to be equal to or approximately equal to the VM voltage, the gate-source voltage V GS is less than its conduction threshold V GS_VTH , the switch tube M2 cannot be turned on, and charging is prohibited.

[0005] The existing zero-volt charging prohibition function is mainly realized by using a pull-down resistor or a pull-down MOS tube as a pull-down device for the CO voltage to pull down the CO voltage. Using a pull-down resistor as a pull-down device is prone to problems such as high static power consumption or slow pull-down speed; and using a pull-down MOS tube as a pull-down device, the pull-down MOS tube must be implemented with a high-voltage thick-gate oxide MOS tube, which has high process requirements, and the high-voltage tube will increase the chip area, increase the mask level, and increase the chip cost. Summary of the invention

[0006] The embodiment of the present invention provides a battery charging drive circuit and a battery protection chip, wherein the pull-down MOS tube can be implemented by using a common low-voltage MOS tube, which has one more selectivity than the prior art. When the embodiment of the present invention uses a low-voltage MOS tube as a CO voltage pull-down device, compared with the traditional thick-gate oxide MOS tube, the area and mask level can be reduced, thereby reducing the chip cost.

[0007] In order to solve the above problems, an embodiment of the present invention discloses a battery charging drive circuit, which is integrated in a battery protection chip, including:

[0008] A zero-volt charging prohibition drive switch is used to be turned on when the battery is in a zero-volt state and is connected to a charger;

[0009] A first voltage divider circuit is connected in series with the zero-volt charge prohibition drive switch and is connected between the power supply terminal and the negative charging voltage access terminal of the battery protection chip;

[0010] The pull-down MOS tube has a drain electrode connected to the charging control terminal of the battery protection chip, and a gate electrode and a source electrode connected via a second resistor in the first voltage divider circuit.

[0011] In an implementation of the present invention, the pull-down MOS transistor is a low-voltage MOS transistor.

[0012] In an implementation of the present invention, the first voltage divider circuit further includes a first resistor connected in series with a second resistor, the first resistor is connected to the power supply terminal via a zero-volt charging prohibition drive switch, and the second resistor is connected to the charging negative voltage access terminal;

[0013] Or, the first voltage divider circuit further includes a third resistor connected in series with the second resistor, the second resistor is connected to the power supply terminal via the zero-volt charging prohibition drive switch, and the third resistor is connected to the charging negative voltage access terminal;

[0014] Alternatively, the first voltage divider circuit also includes a first resistor and a third resistor, the first resistor, the second resistor and the third resistor are connected in series in sequence, the first resistor is connected to the power supply end via a zero-volt charging prohibition drive switch, and the third resistor is connected to the charging negative voltage access end.

[0015] In one implementation of the present invention, it also includes: a zero-volt charging prohibition detection module, which is respectively connected to the power supply terminal, the charging negative voltage access terminal and the battery negative electrode input terminal of the battery protection chip to detect whether the battery is in a zero-volt state and connected to a charger based on the voltage signals of the power supply terminal, the battery negative electrode input terminal and the charging negative voltage access terminal, and output a detection result signal; the zero-volt charging prohibition drive switch is turned on and off based on the detection result signal.

[0016] In an implementation of the present invention, the zero-volt charging prohibition detection module includes: an inverter structure 1 formed by a first PMOS tube and a first NMOS tube with a common gate, and a fourth resistor and a clamping protection circuit 1;

[0017] The inverter structure 1 is connected in series with the fourth resistor and connected between the power supply terminal and the negative charging voltage access terminal. The input terminal of the inverter structure 1 is used to receive the voltage signal of the negative input terminal of the battery, and the output terminal is used to generate a detection result signal.

[0018] The clamp protection circuit 1 is connected between the power supply terminal and the output terminal of the inverter structure 1.

[0019] In an implementation of the present invention, the first NMOS transistor is a low-voltage MOS transistor.

[0020] In an implementation of the present invention, a second clamping protection circuit is also included, and the second clamping protection circuit is connected between the gate and the source of the pull-down MOS tube.

[0021] In an implementation of the present invention, it also includes: a normal charging drive switch controlled by a charging drive signal and an overcharging protection drive switch controlled by an overcharging protection drive signal;

[0022] Wherein, the normal charging drive switch is connected between the power supply terminal and the charging control terminal;

[0023] Among them, the overcharge protection drive switch is used to be connected in series with the first voltage divider circuit and connected between the power supply end and the charging negative voltage access end; or the overcharge protection drive switch is used to be connected in series with the second resistor through the fifth resistor and connected between the power supply end and the charging negative voltage access end.

[0024] In an implementation of the present invention, it further includes: an inverter structure 2;

[0025] The second inverter structure is connected between the power supply end and the battery negative electrode input end of the battery protection chip, the input end inputs an overcharge protection driving signal, and the output end outputs a charging driving signal.

[0026] In an implementation of the present invention, a sixth resistor is further included, and the sixth resistor is connected between the normal charging drive switch and the charging control terminal.

[0027] Based on the same inventive concept, an embodiment of the present invention further discloses a battery protection chip, including the battery charging drive circuit as described in the embodiment of the present invention.

[0028] The embodiments of the present invention include the following advantages:

[0029] The embodiment of the present invention provides a battery charging drive circuit, which is applied to a battery protection chip, including a zero-volt charging prohibition drive switch, a first voltage divider circuit and a pull-down MOS tube. The pull-down MOS tube of the present invention can be implemented by using an ordinary low-voltage MOS tube, which has one more selectivity than the prior art and gets rid of the dependence on the high-voltage thick-gate oxide MOS tube.

[0030] When the embodiment of the present invention uses a low-voltage MOS tube as a pull-down device for the CO voltage, compared with the existing use of a high-voltage thick-gate oxide MOS tube as a pull-down device, it can reduce the area and mask levels, thereby reducing the chip cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention.

[0032] Figure 1 This is a common charging application diagram of a battery protection chip;

[0033] Figure 2 is a schematic structural diagram of a battery charging drive circuit according to an embodiment of the present invention;

[0034] Figure 3 is a schematic structural diagram of a battery charging drive circuit according to an embodiment of the present invention;

[0035] Figure 4 is a schematic structural diagram of a battery charging drive circuit according to an embodiment of the present invention;

[0036] Figure 5 2 is a schematic diagram of the structure of a zero-volt charging prohibition detection module according to an embodiment of the present invention;

[0037] Figure 6 is a schematic structural diagram of a battery charging drive circuit according to an embodiment of the present invention;

[0038] Figure 7 is a schematic structural diagram of a battery charging drive circuit according to an embodiment of the present invention;

[0039] Figure 8 It is a schematic structural diagram of a battery charging drive circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0041] In the following, the terms "second", "first", "XX-one", "XX-two", etc. are only used for convenience of description to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "second", "first", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0042] In the embodiments of the present invention, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. In addition, the term "coupled" can be a direct electrical connection or an indirect electrical connection through an intermediate medium. The term "contact" can be a direct contact or an indirect contact through an intermediate medium.

[0043] In the embodiment of the present invention, "and / or" describes the association relationship of the associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist at the same time, and B exists alone, where A and B may be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0044] The embodiment of the present invention provides a battery charging drive circuit integrated in a battery protection chip, wherein the battery may be a lithium battery.

[0045] In one embodiment of the present invention, the battery charging drive circuit can at least realize the function of prohibiting charging of the battery at zero volt. Figure 2 The battery charging drive circuit includes: a zero-volt charging prohibition drive switch, a first voltage divider circuit and a pull-down MOS tube.

[0046] The embodiment of the present invention adopts a pull-down MOS tube as a pull-down device for the CO voltage, avoiding the problem of high static power consumption or slow pull-down speed when using a pull-down resistor as a pull-down device. Compared with the pull-down MOS tube in the prior art solution, which must be implemented by using a high-voltage thick-gate oxide MOS tube, based on the battery charging drive circuit provided by the embodiment of the present invention, the pull-down MOS tube in the embodiment of the present invention can be implemented by using an ordinary low-voltage MOS tube, which has one more selectivity than the prior art. When the embodiment of the present invention adopts a low-voltage MOS tube as a CO voltage pull-down device, compared with the traditional thick-gate oxide MOS tube, it can reduce the area, reduce the mask level, and thus reduce the chip cost.

[0047] It is worth noting that, although low voltage and high voltage are relative concepts, in this field, technicians in this field have a strong consensus on the distinction between high voltage MOS tubes and low voltage MOS tubes: high voltage MOS tubes usually have higher withstand voltage capability, but large on-resistance, slow switching speed, multiple layers and large area; low voltage MOS tubes have smaller on-resistance, fast switching speed, fewer layers and less area, but limited withstand voltage capability. Structurally, high voltage MOS tubes usually have thicker oxide layers and longer channels, that is, thick gates to withstand higher voltage stress. In addition, the material selection of high voltage MOS tubes is also more stringent to ensure stability and reliability under high voltage. The structure of low voltage MOS tubes is relatively simple, with thin oxide layers and shorter channels, that is, generally thin gates, which helps to increase switching speed and reduce power consumption. Therefore, low voltage MOS tubes and high voltage MOS tubes are very clear in this field. In this application, it can be considered that the withstand voltage of low voltage MOS tubes is lower than that of high voltage MOS tubes in one or more withstand voltage indicators such as DS (drain-source) withstand voltage, DB (drain-bulk) withstand voltage and GS (gate-source) withstand voltage.

[0048] The specific structure of the battery charging drive circuit according to the embodiment of the present invention and the principle that the pull-down MOS tube can be implemented by using a common low-voltage MOS tube are described below.

[0049] In the battery charging drive circuit of the embodiment of the present invention, the zero-volt charging prohibition drive switch is used to be turned on when the battery is in a zero-volt state and is connected to a charger.

[0050] Among them, in the integrated circuit, the switch is usually implemented by a MOS tube. In the embodiment of the present invention, the zero-volt charging prohibition drive switch is implemented by a MOS tube, specifically, a PMOS tube. The zero-volt charging prohibition drive switch is used to turn on when the battery is in a zero-volt state and a charger is connected. It is worth noting that the "zero-volt state" should not be simply and roughly understood as the battery voltage is 0V (volt). In some applications, there are also requirements for the charging voltage based on the charger, which needs to be greater than the set zero-volt chargeable threshold voltage. Therefore, the "zero-volt state" of the battery should be understood as a state where the battery voltage is close to 0V, in which the battery voltage is greater than the set zero-volt chargeable threshold voltage). In other words, the zero-volt state can be understood as a voltage where the battery voltage is zero volts or the power is insufficient to support the normal operation of most circuits inside the chip.

[0051] In specific implementation, the control end of the zero-volt charge prohibition drive switch can be controlled by a detection result signal that characterizes whether the battery is in a zero-volt state and connected to a charger, that is, the zero-volt charge prohibition drive switch can be turned on and off based on the detection result signal. The level of the detection result signal can be used to characterize the state or other states in which the battery is in a zero-volt state and connected to a charger. When the battery is in a zero-volt state and connected to a charger, the detection result signal becomes a valid level, so that the zero-volt charge prohibition drive switch is turned on; in other states, the detection result signal becomes an invalid level, and the zero-volt charge prohibition drive switch is disconnected, that is, not turned on. For example, when the battery is in a zero-volt state and connected to a charger, the level of the detection result signal becomes a low level, and the zero-volt charge prohibition drive switch is turned on; when the battery power can support the normal operation of most circuits inside the chip or the battery is in a zero-volt state but is not connected to a charger, the detection result signal is a high level, and the zero-volt charge prohibition drive switch is turned off.

[0052] In the battery charging drive circuit of an embodiment of the present invention, the first voltage divider circuit is connected in series with the zero-volt charging prohibition drive switch and is connected between the power supply terminal of the battery protection chip (in some descriptions below, the power supply terminal is briefly represented by VDD) and the charging negative voltage access terminal (in some descriptions below, the charging negative voltage access terminal is briefly represented by VM).

[0053] Those skilled in the art should understand that the voltage divider circuit referred to in each embodiment of the present invention is a resistor voltage divider circuit, which is generally composed of multiple resistors in series. When the zero-volt charging prohibition drive switch is turned on, the first voltage divider circuit connects the power supply terminal of the chip with the charging negative voltage access terminal. Since when the battery is in a zero-volt state and a charger is connected, the VDD voltage is zero volts and the VM voltage is a negative voltage, different nodes on the first voltage divider circuit can divide the voltage difference between VDD and VM.

[0054] In the embodiment of the present invention, the first voltage divider circuit may be implemented in different ways:

[0055] Figure 2 An implementation of the first voltage divider circuit is shown, that is, the first voltage divider circuit also includes a first resistor R1 connected in series with a second resistor R2, the first resistor R1 is connected to the power supply terminal VDD via a zero-volt charging prohibition drive switch, and the second resistor R2 is connected to the charging negative voltage access terminal VM. In this implementation, when the zero-volt charging prohibition drive switch is turned on, the gate voltage V G =(VDD-VM)*R1 / (R1+R2), source voltage V S =VM.

[0056] Figure 3 Another implementation of the first voltage divider circuit is shown, that is, the first voltage divider circuit also includes a third resistor R3 connected in series with the second resistor R2, the second resistor R2 is connected to the power supply terminal VDD via a zero-volt charging prohibition drive switch, and the third resistor R3 is connected to the charging negative voltage access terminal VM. In this implementation, when the zero-volt charging prohibition drive switch is turned on, the gate voltage V G =VDD, source voltage V S =(VDD-VM)*R3 / (R2+R3). This implementation is feasible in theory, but in actual circuit applications, the control effect of this result will be poor and is generally not preferred.

[0057] Figure 4 Another implementation of the first voltage divider circuit is shown, that is, the first voltage divider circuit also includes a first resistor R1 and a third resistor R3, the first resistor R1, the second resistor R2 and the third resistor R3 are connected in series in sequence, the first resistor R1 is connected to the power supply terminal via a zero-volt charging prohibition drive switch, and the third resistor R3 is connected to the charging negative voltage access terminal. In this implementation, when the zero-volt charging prohibition drive switch is turned on, the gate voltage V of the MOS tube is pulled down. G =(VDD-VM)*(R2+R3) / (R1+R2+R3), source voltage V S =(VDD-VM)*R3 / (R1+R2+R3).

[0058] It is worth noting that no matter the present invention adopts Figure 2-Figure 4Which first voltage divider circuit is implemented? When the first voltage divider circuit is connected to the zero-volt charging prohibition drive switch, the first voltage divider circuit can also protect the source and drain of the zero-volt charging prohibition drive switch. The first resistor R1, the second resistor R2, and the third resistor R3 are only illustrated as one resistor in each figure, which does not mean that it is only one resistor in practice. In practice, one or more of the first resistor R1, the second resistor R2, and the third resistor R3 can also be implemented with a resistor string (i.e., multiple resistors). Preferably, Figure 4 In the implementation shown, the resistor R3 can prevent the source and drain of the pull-down MOS tube from being broken down, thereby protecting the pull-down MOS tube.

[0059] In the battery charging drive circuit of the embodiment of the present invention, the drain of the pull-down MOS tube is used to connect the charging control terminal of the battery protection chip (hereinafter, the charging control terminal is briefly represented by CO), and its gate and source pass through the second resistor in the first voltage divider circuit.

[0060] In the various drawings of the present invention, the pull-down MOS tube is implemented by an NMOS tube, which is represented by NM4. The gate and source of the pull-down MOS tube are connected through the second resistor in the first voltage divider circuit, that is, the gate and source are respectively connected to different nodes in the first voltage divider circuit, so that after the zero-volt charging prohibition drive switch is turned on, there is a voltage difference between the gate and source of the pull-down MOS tube, so that the pull-down MOS tube can be turned on (i.e., turned on) based on the voltage division of the voltage difference between VDD and VM. In specific applications, the gate voltage and source voltage of the pull-down MOS tube can be controlled separately by adjusting or designing the resistance ratio of each in the first voltage divider circuit to ensure that the pull-down MOS tube is turned on.

[0061] When the pull-down MOS tube is turned on, the source and drain of the pull-down MOS tube will be turned on. Since the drain of the pull-down MOS tube is connected to the charging control terminal of the battery protection chip and the source is connected to the charging negative voltage access terminal, the pull-down MOS tube can pull down the voltage of the charging control terminal (the voltage is briefly represented by the CO voltage in the following text) based on the voltage of the charging negative voltage access terminal (the voltage is briefly represented by the VM voltage in the following text) to achieve that the difference between the CO voltage and the VM voltage is less than the conduction threshold (also called the turn-on threshold) of the switch tube M2. For example, the pull-down MOS tube pulls the CO voltage down to the VM voltage, that is, the voltage CO is equal to the VM voltage, then at this time Figure 1 The gate voltage of the switch tube M2 in the circuit is the VM voltage. Since the source voltage of the switch tube M2 is also the VM voltage, the V GS Equal to 0, the switch tube M2 cannot be turned on, achieving zero volt charging prohibition.

[0062] The embodiment of the present invention uses a first voltage divider circuit to perform a resistor voltage divider on the voltage difference between the power supply terminal and the negative charging voltage access terminal, so that the gate voltage and / or source voltage of the pull-down MOS tube is the voltage divider of the voltage difference between VDD and VM, thereby reducing the gate-source voltage V GS Within a certain range, as long as this range is less than the gate-source breakdown voltage of the low-voltage MOS tube, the pull-down MOS tube can be implemented using an ordinary low-voltage MOS tube, which is particularly suitable for some applications where the VM voltage is not very negative during charging. This structure reduces the V GS The voltage resistance requirement makes it unnecessary for the pull-down MOS tube to use a high-voltage thick-gate oxide MOS tube to withstand the negative high voltage from VDD to VM. Compared with the prior art, the present invention has an additional selectivity when selecting the pull-down MOS tube, and gets rid of the dependence on the high-voltage thick-gate oxide MOS tube. When the embodiment of the present invention uses a low-voltage MOS tube as the CO voltage pull-down device, compared with the traditional thick-gate oxide MOS tube, it can reduce the area, reduce the mask level, and thus reduce the chip cost.

[0063] In a battery charging drive circuit according to a preferred embodiment of the present invention, the pull-down MOS tube is a low-voltage MOS tube.

[0064] Continue to refer Figure 2-4 The battery charging drive circuit of the embodiment of the present invention also includes a zero-volt charging prohibition detection module, which is respectively connected to the power supply terminal, the charging negative voltage access terminal and the battery negative electrode input terminal of the battery protection chip (hereinafter, the battery negative electrode input terminal is briefly represented by VSS) to detect whether the battery is in a zero-volt state and connected to a charger based on the voltage signals of the power supply terminal, the battery negative electrode input terminal and the charging negative voltage access terminal, and output a detection result signal; the zero-volt charging prohibition drive switch is turned on and off based on the detection result signal.

[0065] Among them, the zero-volt charging prohibition detection module can control the level of the detection result signal generated based on the voltage signal control of VDD, VSS and VM, thereby controlling the conduction and disconnection of the zero-volt charging prohibition drive switch. Specifically, when the battery power can support the normal operation of most circuits inside the chip, VDD is a positive voltage, and the voltages of VSS and VM are zero volts. At this time, the detection result signal can be controlled to a high level based on the VDD voltage. When the battery is in a zero-volt state and a charger is connected, the voltages of VDD and VSS are both zero volts, while VM is a negative voltage relative to VSS. At this time, the detection result signal can be controlled to a low level based on the VM voltage. When the battery is in a zero-volt state and is not connected to a charger, the entire internal circuit of the chip does not work.

[0066] It is worth mentioning that the zero-volt charging prohibition detection module can detect whether a charger is connected, indicating that the charging voltage of the charger meets the detection requirements. The charging voltage enables the voltage change of VM to have a gap with VSS, so that the zero-volt charging prohibition detection module can detect it.

[0067] Based on the above working principle, the zero-volt charging prohibition detection module can be implemented using an inverter structure. The VSS voltage signal is the input signal of the inverter structure, and the output end of the inverter structure is used to output the detection result signal. Figure 5 The zero-volt charging prohibition detection module includes: an inverter structure 1 formed by a first PMOS tube PM1 and a first NMOS tube NM1 with a common gate, and includes a fourth resistor R4 and a clamping protection circuit 1; the inverter structure 1 and the fourth resistor R4 are connected in series and connected between the power supply end and the charging negative voltage access end, the input end of the inverter structure 1 is used to receive the voltage signal of the negative electrode input end of the battery, and the output end is used to generate a detection result signal; the clamping protection circuit 1 is connected between the power supply end and the output end of the inverter structure 1.

[0068] Based on the different driving capabilities of the first PMOS tube PM1 and the first NMOS tube NM1 in the inverter structure 1, it is possible to control the detection result signal to a low level or a high level. Specifically, when the battery power can support the normal operation of most circuits inside the chip, VDD is a positive voltage, and the voltages of VSS and VM are zero volts. At this time, the first PMOS tube PM1 is turned on, the first NMOS tube NM1 is turned off, the detection result signal is pulled up by the VDD voltage, and the detection result signal is output as a high level. When the battery is in a zero-volt state and a charger is connected, the voltages of VDD and VSS are both zero volts, while the VM voltage is a negative voltage. At this time, the first PMOS tube PM1 is turned off, the first NMOS tube NM1 is turned on, the detection result signal is pulled down by the VM voltage, and the detection result signal is output as a low level. When the battery is in a zero-volt state and is not connected to a charger, the entire internal circuit of the chip does not work. In practical applications, the driving capability of the first PMOS tube PM1 can be designed to be higher than that of the first NMOS tube NM1. When the battery has power and is connected to a charger, that is, VDD is a positive voltage, VSS is zero volts, and VM is a negative voltage, the first PMOS tube PM1 has a stronger driving capability, so the first PMOS tube PM1 is turned on and the first NMOS tube NM1 is turned off, and the level of the detection result signal is pulled up by the VDD voltage.

[0069] It is worth emphasizing that if only the inverter structure is used to realize the function of the zero-volt charging prohibition detection module, the voltage difference between VM and VSS is large, and the first NMOS tube NM1 needs a thick gate oxide MOS tube with high voltage resistance to meet the circuit requirements. However, the use of thick gate oxide MOS tubes will increase its area and increase the number of mask levels, which increases the wafer cost. Figure 5As shown, the zero-volt charging prohibition detection module of the embodiment of the present invention includes not only an inverter structure 1, but also a fourth resistor R4 and a clamping protection circuit 1. Through the joint action of the fourth resistor R4 and the clamping protection circuit 1, the first NMOS tube NM1 can be implemented by using an ordinary low-voltage MOS tube, which has one more selectivity than the prior art. Of course, preferably, the first NMOS tube is a low-voltage MOS tube.

[0070] The working principle of the fourth resistor R4 and the clamping protection circuit 1 is described below:

[0071] When the battery is at zero volts and connected to a charger, the VM voltage is negative, and the first NMOS tube NM1 is turned on. At this time, the detection result signal is pulled to the source voltage of the first NMOS tube NM1, which is also negative, and the level of the detection result signal becomes a low level.

[0072] If the VM voltage is very negative and the voltage difference between it and VSS becomes very large, the voltage of the detection result signal is also pulled to a very negative value, and the clamping protection circuit 1 will clamp the voltage difference between the VDD voltage and the detection result signal to a fixed value. At this time, a current I flows through the clamping protection circuit 1, and flows through the first NMOS tube NM1 to R4 and finally reaches the charging negative voltage access terminal. Since the drain of the first NMOS tube NM1 is the output terminal of the detection result signal, it can be considered that the maximum voltage difference between the drain of the first NMOS tube NM1 (i.e., the output terminal of the inverter structure 1) and VDD is clamped and fixed; since when the charging negative voltage access terminal is very negative, the first NMOS tube NM1 must work in the linear region, so its source and drain voltages are basically equal, and then it can be considered that the source voltage of the first NMOS tube NM1 and the VDD voltage are also clamped and fixed. When the battery is in a zero-volt state and connected to a charger, the voltages of VSS and VDD are both zero volts, and the gate voltage of the first NMOS tube NM1 is also fixed based on the VSS voltage, which is equivalent to the difference between the gate voltage and the source voltage of the first NMOS tube NM1 being clamped and fixed. In other words, once the voltage difference between VM and VSS reaches the point where the clamping protection circuit 1 can work, the gate-source voltage of the first NMOS tube NM1 is also clamped, which enables the first NMOS tube NM1 to be implemented using a low-voltage NMOS tube.

[0073] Among them, the source voltage of the first NMOS tube NM1 is equal to the VM voltage plus I*R4. Since the gate-source voltage of the first NMOS tube NM1 is also clamped, the source voltage and the VDD voltage are also clamped and fixed. When its gate voltage is 0V, the source voltage is also a fixed value. In different charging applications, the voltage of the connected charger is different, and the negative situation of the VM voltage is also different. When the VM voltage decreases with the application situation, although the current I will increase accordingly, the negative increase in the voltage of VM with the application situation will eventually fall on R4, ensuring that the gate source of the first NMOS tube NM1 implemented using a low-voltage NMOS tube will not be broken down. At the same time, due to the action of the clamping protection circuit 1, the source-drain voltage of the first PMOS tube PM1 and the gate-source voltage of the zero-volt charging prohibition drive switch implemented by the MOS tube will also be clamped, so the clamping protection circuit 1 also protects the first PMOS tube PM1 and the zero-volt charging prohibition drive switch.

[0074] Obviously, based on Figure 5 The design of the zero-volt charging prohibition detection module shown not only enables the first NMOS tube NM1 to be implemented with an ordinary low-voltage MOS tube, and the entire circuit achieves a lower level of mask and a small area, reducing the wafer cost, but also makes the battery protection chip provided by this solution more universal and applicable to chargers with different voltage specifications.

[0075] Optionally, the clamp protection circuit 1 can be implemented by the following structure: the clamp protection circuit 1 includes one or more second PMOS tubes connected in series between the power supply terminal and the output terminal of the inverter structure 1, and the gate and drain of the second PMOS tube are short-circuited. Figure 5 As shown, the clamping protection circuit 1 includes two second PMOS transistors connected in series between the power supply terminal and the output terminal of the inverter structure 1, and the two second PMOS transistors are represented by PM2 and PM3 respectively.

[0076] Similarly, in order to improve the application range of this solution and ensure that the pull-down MOS tube can also be implemented with a low-voltage MOS tube in charging applications where the VM voltage is very negative, refer to Figure 6 The battery charging drive circuit of the embodiment of the present invention may further include a clamping protection circuit 2, which is connected between the gate and source of the pull-down MOS tube. When VM is very negative, the gate-source voltage of the pull-down MOS tube will also be very large, which may exceed its safety threshold and damage it. By designing the clamping protection circuit 2, the gate-source voltage of the pull-down MOS tube can be turned on when it exceeds the triggering threshold of the clamping protection circuit 2, thereby clamping the gate-source voltage of the pull-down MOS tube to ensure that the gate-source voltage difference of the pull-down MOS tube implemented by the low-voltage MOS tube will not be too large and damaged.

[0077] Optionally, the second clamping protection circuit can be implemented by the following structure: the second clamping protection circuit includes one or more second NMOS tubes connected in series between the gate and source of the pull-down MOS tube, and the gate and drain of the second NMOS tube are short-circuited. Figure 6 As shown, the second clamping protection circuit includes two second NMOS transistors connected in series between the gate and the source of the pull-down MOS transistor. The two second PMOS transistors are represented by NM2 and NM3 respectively.

[0078] In another embodiment of the present invention, the battery charging drive circuit can not only realize the battery zero volt charging prohibition function, but also realize the normal charging and overcharge protection functions. Figure 7 and Figure 8 The battery charging drive circuit includes: a zero-volt charging prohibition drive switch, a first voltage divider circuit, a pull-down MOS tube, a normal charging drive switch controlled by a charging drive signal ctrl3, and an overcharging protection drive switch controlled by an overcharging protection drive signal ctrl2.

[0079] Among them, the zero-volt charging prohibition drive switch, the overcharge protection drive switch and the normal charging drive switch are all implemented by MOS tubes, specifically, they can be implemented by PMOS tubes. Figure 7 and Figure 8 In the figure, the zero-volt charging prohibition drive switch is represented by PMOS tube PM4, the overcharge protection drive switch is represented by PMOS tube PM5, the normal charging drive switch is represented by PMOS tube PM6, and the detection result signal is represented by Ctrl1.

[0080] Among them, the connection structure and working principle between the zero-volt charging prohibition driving switch PM4, the first voltage divider circuit and the pull-down MOS tube NM4 can be referred to the previous text and will not be elaborated here.

[0081] In the embodiment of the present invention, the normal charging driving switch PM6 is connected between the power supply terminal and the charging control terminal, and the normal charging driving switch PM6 is turned on and off based on the input charging driving signal ctrl3.

[0082] When the battery power can support the normal operation of most circuits inside the chip, VDD is a positive voltage, the normal charging drive switch PM6 is turned on based on the input charging drive signal ctrl3, and the CO voltage is pulled up by the VDD voltage. For example, the CO voltage is pulled up to equal the VDD voltage, then at this time Figure 1 The gate voltage of the switch tube M2 in the circuit is VDD voltage, and the source voltage of the switch tube M2 is VM voltage, so that the V GS When the voltage is greater than the conduction threshold, the switch tube M2 is turned on to realize charging.

[0083] It is worth noting that, based on the circuit design of the embodiment of the present invention, a non-inverter structure is adopted for controlling the CO voltage to be pulled up to VDD and controlling the CO voltage to be pulled down to VM, that is, the gate of the normal charging drive switch PM6 and the pull-down MOS tube NM4 are not connected together (non-common gate structure), which makes it possible that during charging, even if the VDD voltage gradually rises, before the overcharge protection threshold is reached, the pull-down MOS tube NM4 is always in the off state, and there is no path from VDD to VM, which can reduce the power consumption of the chip during normal charging and improve the charging efficiency of the chip.

[0084] In the embodiment of the present invention, the overcharge protection driving switch PM5 is also connected to the pull-down MOS tube NM4. When the battery voltage exceeds the charging protection threshold, the overcharge protection driving signal ctrl2 is generated to control the overcharge protection driving switch PM5 to be turned on, and then control the pull-down MOS tube NM4 to be turned on, so that the CO voltage is pulled down by the VM voltage. The charging protection threshold can be a charging overcurrent protection threshold or a charging overvoltage protection threshold, etc. Correspondingly, the overcharge protection driving signal ctrl2 can specifically be a charging overcurrent signal or a charging overvoltage signal, which is generated by other modules inside the battery protection chip. The relevant principles can refer to the prior art and are not limited here.

[0085] There are different ways to connect the overcharge protection driving switch PM5 to the pull-down MOS tube.

[0086] Figure 7 An implementation method is shown, in which the battery charging drive circuit also includes a fifth resistor R5; the fifth resistor R5 and the second resistor R2 are connected in series to form a second voltage divider circuit, and the overcharge protection drive switch PM5 is used to be connected in series with the second voltage divider circuit and then connected between the power supply terminal VDD and the charging negative voltage access terminal VM. After the overcharge protection drive switch PM5 is turned on, the pull-down MOS tube NM4 is turned on by dividing the voltage difference between the power supply terminal VDD and the charging negative voltage access terminal VM based on the second voltage divider circuit. The implementation principle is similar to the principle of turning on the pull-down MOS tube NM4 based on the first voltage divider circuit, and will not be elaborated here. It should be noted that, in theory, the voltage dividing function can be achieved by connecting the fifth resistor R5 and the second resistor R2 in series to form a second voltage divider circuit, but in the present application, in addition to the fifth resistor R5 and the second resistor R2, the second voltage divider circuit may also include other resistors, etc., to provide better application effects. Figure 7 In the embodiment, the resistor R3 can also be considered as a part of the second voltage divider circuit to prevent direct damage to the pull-down MOS tube when the VM voltage is too negative.

[0087] Figure 8Another implementation is shown, that is, the overcharge protection drive switch PM5 is used to be connected in series with the first voltage divider circuit and then connected between the power supply terminal VDD and the negative charging voltage access terminal VM. In this implementation, the overcharge protection drive switch PM5 and the zero-volt charge prohibition drive switch PM4 reuse the first voltage divider circuit to drive the pull-down MOS tube NM4 to turn on. By reusing the first voltage divider circuit, the chip area can be reduced.

[0088] It is worth mentioning that Figure 7 The second voltage divider circuit shown is Figure 8 The first voltage divider circuit shown can protect the source and drain of the overcharge protection drive switch PM5.

[0089] Different from the prior art which requires complex circuit design to generate the charging drive signal ctrl3, the embodiment of the present invention provides a simple solution for generating the charging drive signal. Figure 7 and Figure 8 The battery charging drive circuit shown also includes an inverter structure 2, which is connected between the power supply terminal VDD and the battery negative input terminal VSS, the input terminal inputs an overcharge protection drive signal ctrl2, and the output terminal outputs a charging drive signal ctrl3.

[0090] by Figure 7 Taking the circuit shown as an example, the working process of the zero-volt charging prohibition drive switch PM4, the overcharge protection drive switch PM5 and the normal charging drive switch PM6 is explained.

[0091] When the battery still has power, that is, the voltage difference between VDD and VSS can make most of the internal circuits work normally, then when the charger is connected for charging, the detection result signal ctrl1 controls the zero-volt charging prohibition drive switch PM4 to turn off (i.e. disconnect), and the overcharge protection drive signal ctrl2 defaults to a high level to control the overcharge protection drive switch PM5 to turn off, the VM voltage is near zero volts, and the pull-down MOS tube NM4 is blocked; the overcharge protection drive signal ctrl2 passes through the inverter structure 2 and outputs a low-level charging drive signal ctrl3 to control the normal charging drive switch PM6 to turn on, so that the CO voltage rises to VDD, which can drive the external switch tube used to control charging to turn on, thereby realizing charging.

[0092] When the battery voltage exceeds the charging protection threshold or the charging current reaches the charging overcurrent threshold, that is, when the overcharge protection is triggered, the overcharge protection drive signal ctrl2 becomes a low level, and the level effectively controls the overcharge protection drive switch PM5 to turn on. The overcharge protection drive signal ctrl2 outputs a high level charging drive signal ctrl3 through the inverter structure 2, thereby controlling the normal charging drive switch PM6 to turn off. At this time, the detection result signal ctrl1 controls the zero-volt charge prohibition drive switch PM4 to turn off, pulling down the gate voltage V of the MOS tube NM4.G =(VDD-VM)*(R2+R3) / (R5+R2+R3), source voltage V S =(VDD-VM)*R3 / (R5+R2+R3), by designing the appropriate resistance ratio of R5, R2, and R3, V G With V S The voltage of the gate terminal of NM4 is greater than the conduction threshold of the pull-down MOS tube NM4, so that the pull-down MOS tube NM4 is turned on to pull the CO voltage to the VM voltage, turning off the external switch tube used to control charging, and then turning off the charging circuit. At the same time, when the voltage difference between VDD and VM is within a certain range, the gate terminal voltage of NM4 can be limited to a reasonable range by reasonably adjusting R5 and R2, so that NM4 can use a low-voltage MOS tube to save costs.

[0093] When the battery voltage drops to zero volt, the overcharge protection drive signal ctrl2 and the charge drive signal ctrl3 are digital logic signals with VDD and VSS as power supply and ground, so they are both 0 at this time, and the overcharge protection drive switch PM5 and the normal charge drive switch PM6 are not turned on; at this time, the charger is connected, the VM voltage is negative, the first NMOS tube NM1 is turned on, the detection result signal ctrl1 controls the zero volt charge prohibition drive switch PM4 to turn on, and the first voltage divider circuit divides the voltage between VDD and VM to pull down the gate voltage V of the MOS tube NM4. G =(VDD-VM)*(R2+R3) / (R1+R2+R3), source voltage V S =(VDD-VM)*R3 / (R1+R2+R3), at this time V GS =V G -V S >The turn-on threshold of the pull-down MOS tube NM4. The pull-down MOS tube NM4 is turned on to pull down the CO voltage based on the VM voltage, so that the CO voltage is equal to or approximately equal to the VM voltage. At this time, the CO voltage can drive the external switch tube used to control charging to turn off, thereby completing the zero-volt charging prohibition function.

[0094] In the embodiment of the present invention, continue to refer to Figure 7 The battery charging drive circuit may further include a sixth resistor R6, which is connected between the normal charging drive switch PM6 and the charging control terminal CO. The resistor R6 can play a current limiting role, on the one hand protecting the source and drain of the normal charging drive switch PM6 and the charging control terminal CO, and on the other hand playing an ESD (Electro-Static discharge) protection role.

[0095] The embodiment of the present invention further provides a battery protection chip, which includes a power supply terminal VDD, a battery negative electrode input terminal VSS, a charging negative voltage access terminal VM, a charging control terminal CO, and a battery charging drive circuit of the embodiment of the present invention, wherein the battery charging drive circuit is respectively connected to the power supply terminal VDD, the battery negative electrode input terminal VSS, the charging negative voltage access terminal VM, and the charging control terminal CO. The specific connection method and the relevant structure and working principle of the battery charging drive circuit can be referred to the above, and will not be elaborated here.

[0096] The battery protection chip of the embodiment of the present invention not only realizes the zero-volt charging prohibition function, but also, compared with the prior art, the circuit for realizing the zero-volt charging prohibition function and the circuit for realizing the overcharge protection drive in the present chip can share most of the circuits, which can effectively save the chip area, reduce the mask level, and save the cost. At the same time, the present invention can also select a low-voltage MOS tube as a pull-down device for the CO voltage to reduce the dependence on the traditional high-voltage thick-gate oxide MOS tube.

[0097] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0098] The technical solution provided by the present invention is described in detail above. The principle and implementation mode of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the present invention, and the content of this specification should not be understood as limiting the present invention. At the same time, for those skilled in the art, according to the present invention, there will be different forms of changes in the specific implementation mode and application scope. It is not necessary and impossible to list all the implementation modes here, and the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A battery charging drive circuit, characterized in that: Integrated into the battery protection chip, including: A zero-volt charging prohibition drive switch is used to be turned on when the battery is in a zero-volt state and is connected to a charger; A first voltage divider circuit is connected in series with the zero-volt charge prohibition drive switch and is connected between the power supply terminal and the negative charging voltage access terminal of the battery protection chip; The pull-down MOS tube has a drain electrode connected to the charging control terminal of the battery protection chip, and a gate electrode and a source electrode connected via a second resistor in the first voltage divider circuit.

2. The battery charging drive circuit according to claim 1, characterized in that: The pull-down MOS tube is a low-voltage MOS tube.

3. The battery charging drive circuit according to claim 1, characterized in that: The first voltage divider circuit further includes a first resistor connected in series with the second resistor, the first resistor is connected to the power supply terminal via the zero-volt charging prohibition drive switch, and the second resistor is connected to the charging negative voltage access terminal; Or, the first voltage divider circuit further includes a third resistor connected in series with the second resistor, the second resistor is connected to the power supply terminal via the zero-volt charging prohibition drive switch, and the third resistor is connected to the charging negative voltage access terminal; Alternatively, the first voltage divider circuit also includes a first resistor and a third resistor, the first resistor, the second resistor and the third resistor are connected in series in sequence, the first resistor is connected to the power supply end via the zero-volt charging prohibition drive switch, and the third resistor is connected to the charging negative voltage access end.

4. The battery charging drive circuit according to claim 1, characterized in that: Also includes: Zero volt charging prohibition detection module, The zero-volt charging prohibition detection module is connected to the power supply terminal, the charging negative voltage access terminal and the battery negative electrode input terminal of the battery protection chip respectively, so as to detect whether the battery is in a zero-volt state and connected to a charger based on the voltage signals of the power supply terminal, the battery negative electrode input terminal and the charging negative voltage access terminal, and output a detection result signal; The zero-volt charge prohibition drive switch is turned on and off based on the detection result signal.

5. The battery charging drive circuit according to claim 4, characterized in that: The zero-volt charging prohibition detection module includes: an inverter structure 1 formed by a first PMOS tube and a first NMOS tube with a common gate, and a fourth resistor and a clamping protection circuit 1; The inverter structure 1 is connected in series with the fourth resistor and connected between the power supply terminal and the negative charging voltage access terminal. The input terminal of the inverter structure 1 is used to receive the voltage signal of the negative input terminal of the battery, and the output terminal is used to generate the detection result signal. The clamp protection circuit 1 is connected between the power supply terminal and the output terminal of the inverter structure 1.

6. The battery charging drive circuit according to claim 5, characterized in that: The first NMOS tube is a low-voltage MOS tube.

7. The battery charging drive circuit according to claim 1 or 2, characterized in that: It also includes a second clamping protection circuit, which is connected between the gate and the source of the pull-down MOS tube.

8. The battery charging drive circuit according to claim 1, characterized in that: Also includes: A normal charging drive switch controlled by a charging drive signal and an overcharging protection drive switch controlled by an overcharging protection drive signal; Wherein, the normal charging drive switch is connected between the power supply terminal and the charging control terminal; Among them, the overcharge protection drive switch is used to be connected in series with the first voltage divider circuit and connected between the power supply end and the charging negative voltage access end; or the overcharge protection drive switch is used to be connected in series with the second resistor via a fifth resistor and connected between the power supply end and the charging negative voltage access end.

9. The battery charging drive circuit according to claim 8, characterized in that: Also included: inverter structure 2; The second inverter structure is connected between the power supply end and the battery negative electrode input end of the battery protection chip, the input end inputs the overcharge protection driving signal, and the output end outputs the charging driving signal.

10. The battery charging drive circuit according to claim 8, characterized in that: It also includes a sixth resistor, which is connected between the normal charging drive switch and the charging control terminal.

11. A battery protection chip, characterized in that: The invention comprises a battery charging drive circuit as described in any one of claims 1 to 10.

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