Battery protection

Abstract

A battery protection system is described. The system includes a battery and a load / charge port configured to be coupled to a load or a battery charger. A main protection switch and a secondary protection switch are coupled between the battery and the load / charge port. The system also includes a main protection circuit configured to sense the voltage across the battery and control the main protection switch based on the sensed voltage. The secondary protection circuit is also configured to sense the voltage across the battery and control the secondary protection switch based on the sensed voltage. The main and secondary protection circuits are arranged in parallel across the battery. A method for operating battery protection and an apparatus including the battery protection system are also disclosed.

Description

Background Technology

[0001] Consumer appliances such as electric toothbrushes, vacuum cleaners, and hair dryers can be powered by rechargeable batteries. Rechargeable batteries can power appliance loads, such as motors, during use. When not in use, the batteries can be recharged. These operations can be controlled by battery protection circuitry. Battery protection circuitry can perform various tasks, such as discharge control, battery charger detection, and charging control. This can be achieved by controlling one or more switches located between the battery and the load or battery charger. Battery protection circuitry can also perform various protection functions, such as undervoltage protection. Summary of the Invention

[0002] In a first aspect, this disclosure provides a battery protection system, comprising: a battery; a load / charging port configured to be coupled to a load or a battery charger; a main protection switch coupled between the battery and the load / charging port; a secondary protection switch coupled between the battery and the load / charging port; a main protection circuit configured to sense a voltage across the battery and control the main protection switch based on the sensed voltage; and a secondary protection circuit configured to sense a voltage across the battery and control the secondary protection switch based on the sensed voltage; wherein the main protection circuit and the secondary protection circuit are arranged in parallel across the battery.

[0003] In modern electronic devices, battery protection systems may require two protection circuits. The primary and secondary protection circuits can perform various functions, including overcurrent protection, overtemperature protection, and overvoltage and undervoltage protection. Specifically, the protection circuits can prevent battery discharge when the battery voltage drops below a specific voltage. In prior art protection systems, the primary and secondary protection circuits can be connected in series, with the secondary protection switch coupled between the primary protection circuit and the battery. In this arrangement, the primary protection circuit senses the battery voltage through the secondary protection switch, meaning that the battery voltage cannot be sensed accurately. This can lead to errors in the sensed voltage, potentially causing system failure. In the first aspect of this disclosure, the primary and secondary protection circuits can be coupled to the battery in parallel. This allows both the primary and secondary protection circuits to sense the battery voltage accurately, meaning that the sensed battery voltage is less likely to include errors and reduces the likelihood of system failure.

[0004] The main protection circuit can be coupled across the battery between the battery and both the main and secondary protection switches. By coupling the main protection circuit to a point in the circuit between the battery and the protection switches, there are no active devices between the battery protection circuit and the battery. This allows the battery protection circuit to sense the battery voltage more accurately. When sensing the battery voltage, the battery protection circuit can consider passive components such as resistors and capacitors, as they are fixed. However, active devices such as switches can change their values ​​depending on their state. For example, in some examples known in the prior art, the main protection circuit senses the battery voltage through the secondary protection switch. When the switch is open and closed, this causes a significant change in the battery voltage. For example, depending on the switch state, a bandgap voltage of 0.7V can be added to or removed from the sensed voltage. The secondary protection circuit can be configured in the same manner.

[0005] The main protection circuit can be configured to detect the presence of a battery charger coupled to the load / charging port. The main protection circuit may include a main ground connection that can be coupled to the negative terminal of the battery. Thus, the main protection circuit can be arranged in parallel with the battery, and a secondary protection switch is located between the common ground connection and the load / charging port.

[0006] The primary protection circuit may include a battery voltage sensing connection coupled to the positive terminal of the battery. The primary protection circuit may also be configured to sense the battery voltage via the battery voltage sensing connection and a primary ground connection. The primary protection circuit may include two connections for sensing the battery voltage. These connections may be coupled to the positive and negative battery terminals to enable accurate sensing of the battery voltage. The secondary protection circuit may include corresponding connections configured in the same manner.

[0007] The main protection circuit may include a battery charger detection connection coupled to the load / charging port. The main protection circuit can also be configured to detect the battery charger via both the battery charger detection connection and the main ground connection. By coupling two battery voltage sensing connections across the battery terminals, the main protection circuit can sense the battery voltage more accurately. Passive components can be located between the battery protection circuit and the battery without adversely affecting battery sensing. These components can be precisely compensated.

[0008] The main protection circuit may include a main ground connection, and the secondary protection circuit may include a secondary ground connection. Both the main and secondary ground connections may be coupled to the negative terminal of the battery.

[0009] The main protection switch can be coupled between the first terminal of the battery and the first terminal of the load / charge port, and the secondary protection switch can be coupled between the second terminal of the battery and the second terminal of the load / charge port. The first terminal can be a positive terminal, and the second terminal can be a negative terminal.

[0010] The primary protection circuit can be a first integrated circuit, and the secondary protection circuit can be a second integrated circuit. Due to local regulations or other safety requirements, it may be necessary to use two separate integrated circuits (ICs). The second protection circuit IC may include bypass circuitry, meaning that the primary and secondary protection circuits can be connected in parallel with the battery. Therefore, the second IC provides both the secondary protection circuitry and the bypass circuitry, enabling the system to accurately sense the battery voltage using both ICs while also detecting the presence of the battery charger.

[0011] The main protection circuit can also be configured to disconnect the main protection switch when the battery voltage drops below a first threshold voltage. The secondary protection circuit can also be configured to disconnect the secondary protection switch when the battery voltage drops below a second threshold voltage. The second threshold voltage can be less than the first threshold voltage.

[0012] When the battery voltage drops below a first threshold, the main protection circuit prevents the battery from discharging into the load. The first threshold can be a voltage below which the electronic device may malfunction. When the battery reaches a lower second threshold voltage, the secondary protection circuit prevents current leakage from the battery. This can occur if the electronic device is stored unused for an extended period. The secondary protection circuit prevents the battery from being completely depleted.

[0013] Battery protection systems can also include a resistor-capacitor (RC) network located between the battery voltage sensing connection and the battery positive terminal. This arrangement can be used to provide filtering or current limiting to protect the main protection circuitry. This passive component can be incorporated into the main protection circuitry, allowing for accurate sensing of the battery voltage. Secondary protection circuitry can also utilize the RC network.

[0014] The main protection circuit can be further configured to detect the presence of a battery charger coupled to the load / charging port and control the main protection switch based at least in part on the presence of the battery charger.

[0015] In addition to providing undervoltage battery protection, the main protection circuit can detect the presence of the battery charger and control the main protection switch to control battery charging.

[0016] The battery protection system may also include a bypass circuit coupled between the battery and the load / charging port. In a first mode, the secondary protection switch may be closed, and the main protection circuit may also be configured to detect the presence of the battery charger via a main charger detection current path including the secondary protection switch. In a second mode, the secondary protection switch may be open, and the main protection circuit may also be configured to detect the presence of the battery charger via a secondary charger detection current path including the bypass circuit.

[0017] Because the main protection circuit and the secondary protection circuit are arranged in parallel with respect to the battery, the secondary protection switch is located between the main protection circuit and the load / charging port. When the secondary protection switch is closed, a current loop can be formed between the main protection circuit and the battery charger via the secondary protection switch. This allows the main protection circuit to detect the presence of the battery charger. However, when the battery voltage drops below a second threshold, the secondary protection switch opens. This interrupts the current loop between the main protection circuit and the battery charger. To solve this problem, a bypass circuit is coupled between the battery and the load / charging port. When the secondary protection switch is open, a secondary charger detection current loop is formed through the bypass circuit, allowing the main protection circuit to detect the presence of the battery charger.

[0018] The bypass circuit may include at least one bypass resistor and at least one bypass switch, and in a second mode of operation, at least one bypass switch may be closed. The second mode of operation may be an undervoltage operation mode in which the battery voltage drops below an undervoltage threshold. The bypass circuit may be coupled between the positive terminal of the battery and the negative terminal of the load / charge port. The secondary protection circuit may include the bypass circuit. The secondary charger sense current path may also include / pass through the battery. By providing a secondary protection circuit with a resistor network acting as a bypass circuit, the secondary protection circuit itself provides a secondary charger sense current loop, thereby reducing the complexity of the battery protection system.

[0019] The main protection circuit can also be configured to close the main protection switch when a battery charger is detected, so as to allow the battery charger to charge the battery.

[0020] The system can be configured to form a charging current loop via a primary protection switch and a secondary protection switch during charging, and to allow current to flow through the body diode of the secondary protection switch when the secondary protection switch is open. The switch can be a transistor including a body diode, so that the battery can be charged even when the switch is open.

[0021] In a second aspect, this disclosure provides a method for operating the battery protection system as described above, comprising: sensing a voltage across the battery using a main protection circuit; sensing a voltage across the battery using a secondary protection circuit; controlling a main protection switch using the main protection circuit based on the voltage sensed by the main protection circuit; and controlling a secondary protection switch using the secondary protection circuit based on the voltage sensed by the secondary protection circuit.

[0022] The method may further include using a main protection circuit to disconnect a main protection switch when the battery voltage drops below a first threshold voltage. The method may also include using a secondary protection circuit to disconnect a secondary protection switch when the battery voltage drops below a second threshold voltage. The second threshold voltage may be less than the first threshold voltage.

[0023] The method may further include: when the secondary protection switch is closed, using the main protection circuit to detect the presence of the battery charger via the main charger detection current path including the secondary protection switch; and closing the main protection switch to enable the battery to be charged.

[0024] The method may further include: when the secondary protection switch is open, using the main protection circuit to detect the presence of the battery charger via a secondary charger detection current path including a bypass circuit; and closing the main protection switch to enable the battery to be charged.

[0025] In a third aspect, this disclosure provides an electronic appliance including the battery protection system described above.

[0026] The electronic appliance may also include: a battery charger docking station configured to receive a battery charger and coupled to a load / charging port; a load coupled to the load / charging port; and a user interface coupled to a battery protection system and configured to control the discharge of the battery to the load. The load may be an electric motor.

[0027] The main protection switch can be two main protection switches, including a main charging switch and a main discharging switch. Similarly, the secondary protection switch can be two secondary protection switches, including a secondary charging switch and a secondary discharging switch. The two main protection switches can be coupled to the main protection circuit, and the two secondary protection switches can be coupled to the secondary protection circuit. The charging switch is closed during charging operation, and the discharging switch is closed during discharging operation. The charging and discharging switches can have opposite polarities, meaning that the charging switch blocks current flowing in one direction, and the discharging switch blocks current flowing in the opposite direction. Both switches include a body diode, meaning they can carry current flowing in one direction even when open.

[0028] A battery protection system may include a single bidirectional current path for charging and discharging the battery. This current path may include a primary protection switch and a secondary protection switch. Therefore, the system may utilize paired unipolar transistors, such as MOSFETs, or it may utilize a bidirectional switch.

[0029] In another aspect of the invention, a battery protection system is disclosed, which can be configured to perform battery charger detection. The system may include a charger detection circuit configured in use to form a main charger detection current loop with the battery charger. The charger detection circuit may form part of a main protection circuit. The main charger detection current loop may be a current path including the main protection circuit and a secondary protection switch. The battery protection system may further include a battery protection circuit that disconnects the battery from the battery charger port when the battery is in an undervoltage condition. The battery protection circuit may form part of a secondary protection circuit. The battery protection circuit may be configured to disconnect the battery from the battery charger port using a secondary protection switch. When the battery is disconnected from the battery charger port, the main charger detection current loop is blocked by the disconnected secondary protection switch. The system may be further configured to provide a secondary charger detection current path between the charger detection circuit and the battery charger when the battery is in an undervoltage condition, thereby enabling the charger detection circuit to detect the battery charger. The secondary charger detection current path may include the battery and a bypass circuit, which forms part of the secondary protection circuit to avoid disconnecting the secondary protection switch.

[0030] Battery protection systems can be particularly useful in smaller electronic devices, such as oral care devices (e.g., electric toothbrushes). Alternatively, they can also be used in other electronic appliances, including floor care appliances (e.g., stick vacuum cleaners) or hair care appliances (e.g., hair dryers). Attached Figure Description

[0031] Figure 1 This is a system diagram illustrating a battery protection system according to a first embodiment of the present disclosure;

[0032] Figure 2 It is shown Figure 1 A flowchart of the first operating method of the system shown;

[0033] Figure 3 It is shown Figure 1 A flowchart of the second operation method of the system shown;

[0034] Figure 4 It is shown Figure 1 The diagram shows the battery protection system during the second operating method.

[0035] Figure 5 It is shown Figure 1 Another system diagram of the battery protection system shown during the second operating method; and

[0036] Figure 6 This is a system diagram illustrating a battery protection system according to a second embodiment of the present disclosure. Detailed Implementation

[0037] Figure 1 A battery protection system 100 according to an embodiment of the present disclosure is shown. The battery protection system 100 includes a battery 102, which may be a rechargeable battery. The battery 102 may be a lithium-ion rechargeable battery, or any other suitable rechargeable battery technology may be used. The battery 102 may be a single-cell device or a multi-cell device. The battery protection system 100 is configured to control the charging and discharging of the battery 102. Additionally, the battery protection system 100 may be configured to perform various protection mechanisms, such as undervoltage protection, overvoltage protection, and thermal protection.

[0038] Battery 102 is coupled to a pair of battery terminals 104A and 104B. The battery terminals include a positive battery terminal 104A and a negative battery terminal 104B. Battery protection system 100 may also include a load / charge port configured to be coupled to a load or a battery charger. The battery charger may be a wireless charger, and the load / charge port may be coupled to a wireless charging interface. The load / charge port includes a positive load / charge terminal 106A and a negative load / charge terminal 106B. Battery protection system 100 may be integrated into a consumer appliance, such as a vacuum cleaner or hair dryer, in which case the load / charge port may be coupled to the motor of the appliance. The consumer appliance may include a user interface to control the discharge of battery 102 to a load. For clarity, Figure 1 The user interface is not shown. Battery 102 can operate within a range of voltages. In this embodiment, battery 102 is rated to operate at up to 4.35V. This is a typical voltage for lithium-ion batteries used in consumer electronics.

[0039] Positive battery terminal 104A is coupled to positive load / charge terminal 106A via positive power rail 108A. Negative battery terminal 104B is coupled to negative load / charge terminal 106B via negative power rail 108B. To control the charging and discharging of battery 102, a pair of main protection switches are provided along positive power rail 108A. The main protection switches include a main charging switch 110A and a main discharging switch 110B. Additionally, a pair of secondary protection switches are provided along negative power rail 108B. The secondary protection switches include a secondary charging switch 110C and a secondary discharging switch 110D. The main and secondary protection switches can be MOSFETs or other suitable transistors or switches. As described above, the battery protection system 100 can be used to control the charging and discharging of battery 102. The current flow direction along positive power rail 108A and negative power rail 108B will vary depending on the operating mode. Since MOSFETs are unipolar devices, two switches are required along each power rail, each with opposite polarities. In an alternative embodiment, bidirectional transistors can be used, in which case only a single device will be required along each power rail. In addition, the battery protection system 100 can be configured to be used only for charging the battery 102, in which case only a single unipolar switch may be required.

[0040] The battery protection system 100 also includes a main protection circuit 112A and a secondary protection circuit 112B. Due to electrical regulations in some countries, or to provide more advanced protection routines, two protection circuits may be required. The main protection circuit 112A is coupled to main protection switches 110A and 110B. The secondary protection circuit 112B is coupled to secondary protection switches 110C and 110D. Although the operational differences between the main and secondary protection circuits will become apparent in the remainder of this specification, both circuits can also perform certain common functions, such as undervoltage protection, overvoltage protection, and thermal protection. Furthermore, the main protection circuit 112A and the secondary protection circuit 112B can be implemented as separate integrated circuits. Each circuit may include various pins through which switches can be controlled and various voltages and currents can be sensed. Although separate integrated circuits are used in this embodiment, the same functionality can be achieved using discrete circuit components.

[0041] The main protection circuit 112A includes a charging control pin 114A coupled to the main charging switch 110A and a discharging control pin 114B coupled to the main discharging switch 110B. Additionally, the main protection circuit 112A includes a battery sensing pin / battery voltage sensing connection 114C and a ground pin / main ground connection 114D. The battery sensing pin 114C is coupled to the positive battery terminal 104A. The ground pin 114D is coupled to the negative battery terminal 104B. These connections enable the main protection circuit 112A to sense the voltage of the battery 102.

[0042] The main protection circuit 112A is connected in parallel with the battery 102, using the battery sensing pin 114C and the ground pin 114D to sense the voltage of the battery 102. Furthermore, the battery sensing pin 114C and the ground pin 114D are connected between the battery 102 and the main protection switch 110A and the secondary protection switch 110d. It should be noted that... Figure 1 In this circuit, there are no passive components between the main protection circuit 112A and the battery 102. However, passive components can be provided between the battery 102 and the main protection circuit 112A, for example, to provide current limiting, while still allowing the main protection circuit 112A to accurately measure the voltage of the battery 102. This is because the value of any passive component can be taken into account by the main protection circuit 112A. Furthermore, because the battery sensing pin 114C and the ground pin 114D are coupled between the battery 102 and the main protection switch 110A and the secondary protection switch 110d, there are no active components located between the battery 102 and the main protection circuit 112A. Since the voltage drop across active components can vary depending on their state (e.g., the 0.7V bandgap voltage in a transistor), avoiding such components between the main protection circuit 112A and the battery 102 improves the ability of the main protection circuit 112A to accurately measure the voltage of the battery 102.

[0043] The main protection circuit 112A also includes a charger sensing pin / battery charger detection connection 114E, which is coupled to the positive load / charging terminal 106A. The charger sensing pin 114E is used for charger detection.

[0044] The secondary protection circuit 112B includes a charging control pin 116A coupled to the secondary charging switch 110C and a discharging control pin 116B coupled to the secondary discharging switch 110D. Additionally, the secondary protection circuit 112B includes a battery sensing pin 116C and a ground pin / secondary ground connection 116D. The battery sensing pin 116C is connected to the positive battery terminal 104A. The ground pin 116D is coupled to the negative battery terminal 104B. These connections enable the secondary protection circuit 112B to sense the voltage of the battery 102.

[0045] The secondary protection circuit 112B is connected in parallel with the battery 102, using the battery sensing pin 116C and the ground pin 116D to sense the voltage of the battery 102. Furthermore, the battery sensing pin 116C and the ground pin 116D are connected between the battery 102 and the main protection switch 110A and the secondary protection switch 110d. It should be noted that... Figure 1In this circuit, there are no passive components between the secondary protection circuit 112B and the battery 102. However, passive components can be provided between the battery 102 and the secondary protection circuit 112B, for example, to provide current limiting or filtering, while still enabling the secondary protection circuit 112B to accurately measure the voltage of the battery 102. This is because the value of any passive component can be taken into account by the secondary protection circuit 112B. Furthermore, because the battery sensing pin 116C and the ground pin 116D are coupled between the battery 102 and the main protection switch 110A and the secondary protection switch 110d, there are no active components located between the battery 102 and the secondary protection circuit 112B. Since the voltage drop across active components can vary depending on their state (e.g., the 0.7V bandgap voltage in a transistor), avoiding such components between the secondary protection circuit 112B and the battery 102 improves the ability of the secondary protection circuit 112B to accurately measure the voltage of the battery 102.

[0046] The secondary protection circuit 112B also includes a charger sensing pin 116E coupled to the negative load / charging terminal 106B. This pin can be used by the secondary protection circuit 112B to perform electrostatic discharge detection or charger polarity fault. The secondary protection circuit 112B also includes a bypass circuit 118. The bypass circuit 118 provides a switchable current path between the battery sensing node 116C and the charger sensing pin 116E. The bypass circuit 118 can be a switch and resistor connected in series between the battery sensing pin 116C and the charger sensing pin 116E.

[0047] It should be noted that, depending on the implementation of the circuit, various passive circuit components, such as resistors, capacitors, and inductors, can be used at various points in the circuit. Such components can be used for current sensing or current limiting. Passive components can be provided as discrete components within the circuit, or they can be provided as integrated components within integrated circuits constituting the main protection circuit and the secondary protection circuit. For clarity, these components are omitted in this embodiment.

[0048] The battery protection system 100 is configured to prevent over-discharge of the battery 102. This is achieved by sensing when the battery voltage drops below one or more thresholds and disconnecting it from the load / charging port. This is known as undervoltage protection.

[0049] Figure 2This is a flowchart illustrating the process that occurs when battery 102 discharges. In normal operating mode, all main protection switches 110A and secondary protection switches 110d are closed, and battery 102 can discharge to the load via the load / charge port (S200). As mentioned above, the maximum battery voltage can be 5V, and the operating voltage range can be 2.5V to 5V. These voltages are not intended to be limiting, and the actual operating range will depend on the battery type and the appliance powered by battery 102. Battery protection system 100 has an operating voltage range, with a minimum operating voltage and a maximum operating voltage. In this case, the minimum operating voltage is 2.5V, and the maximum operating voltage is 5V.

[0050] The main protection circuit 112A and the secondary protection circuit 112B monitor the battery voltage, and this information is used to control the operation of the main protection switch and the secondary protection switch. When the battery voltage drops below the minimum operating voltage / first threshold voltage, the main protection circuit 112A disconnects the main protection switches 110A and 110B (S202). This prevents the battery 102 from discharging further to the load. This is called undervoltage protection, and the minimum operating voltage is also called the first undervoltage threshold. At this time, the battery 102 may not be used to power the load until it has been charged. In this embodiment, when the main protection switches 110A and 110B are open and the secondary protection switches 110C and 110D are closed, the negative load / charging terminal 106B is connected to the negative battery terminal 104B or grounded. Therefore, the negative load / charging terminal 106B is at 0V. When the positive load / charging terminal 106A is isolated from the positive battery terminal 104A by the disconnected main protection switches 110A and 110B, it floats to the same voltage as the negative load / charging terminal 106B, i.e., 0V.

[0051] Even when battery 102 is disconnected from the load via main protection switches 110A and 110B, current leakage may still occur through the negative battery terminal 104B. Secondary protection switches 110C and 110D initially remain closed, allowing a current leakage path toward the negative load / charging terminal 106B. This type of current leakage is typically low enough that it will not significantly deplete the battery in a short period. However, over time, battery 102 may discharge to a point where it can no longer be recharged. For example, if an appliance including the battery protection system 100 is stored for an extended period, current leakage from battery 102 may render the battery unusable.

[0052] Therefore, when the battery voltage drops below the second undervoltage threshold / second threshold voltage, the secondary protection circuit 112B disconnects the secondary discharge switch 110D (S204). This prevents the battery 102 from discharging via the negative load / charging terminal 106B. In this embodiment, the second undervoltage threshold is 2.35V. In this case, the secondary charging switch 110C remains closed. It is not necessary to disconnect the secondary charging switch 110C to prevent current leakage, and closing this switch, as will be described below, facilitates battery charging, which may occur later.

[0053] In addition to sensing the battery voltage, the main protection circuit 112A also performs battery charger detection via the charger sensing pin 114E. To perform battery charger detection, the main protection circuit 112A needs to be connected to both the positive load / charging terminal 106A and the negative load / charging terminal 106B. When both secondary protection switches are closed (i.e., after the battery voltage drops below a first undervoltage threshold but not a second undervoltage threshold), the ground pin 114D can form a current path to the negative load / charging terminal 106B. Therefore, in this case, the main protection circuit 112A can detect when a battery charger is present. However, once the secondary discharge switch 110D is open, a current path is no longer formed between the ground pin 114D and the negative load / charging terminal 106B. Therefore, the secondary protection circuit 112B includes a bypass circuit 118.

[0054] When the second undervoltage threshold is exceeded, the secondary protection circuit 112B closes the bypass circuit 118, creating a current path between the battery sensing pin 116C and the charger sensing pin 116E (S206). The bypass circuit can be a switch and a resistor connected in series between the battery sensing pin 116C and the charger sensing pin 116E. The resistor can have a value in the range of 250kΩ to 3500kΩ. In this embodiment, the resistor has a value of 1250kΩ. The resistor can be a resistor network rather than a single resistor.

[0055] After the battery voltage drops below the second undervoltage threshold, the secondary discharge switch 110D opens, and the bypass circuit 118 switches to a closed circuit. When the battery voltage drops below the second undervoltage threshold (e.g., to 2.25V), the negative load / charge terminal 106B is pulled up to the same voltage as the positive battery terminal 104A due to the current path formed through the bypass circuit 118 in the secondary protection circuit 112B. Additionally, because the positive load / charge terminal 106A remains isolated from the positive battery terminal 104A but is coupled to the negative load / charge terminal 106B via the load, it also floats to the battery voltage (e.g., 2.25V).

[0056] Figure 3It is a flowchart showing the process that occurs when the charger is connected to the load / charging port when the battery voltage is below the second undervoltage threshold.

[0057] A charger (not shown) is coupled across the load / charge port (S300). The charger can be, for example, a 5V battery charger suitable for use with lithium-ion rechargeable batteries. The battery voltage is initially maintained at 2.25V. The negative load / charge terminal 106B is still coupled to the positive battery terminal 104A via the bypass circuit 118, and therefore also maintained at 2.25V. The battery charger adds 5V to this value, bringing the positive load / charge terminal 106A to 7.25V. This voltage can then be sensed by the charger sensing pin 114E. However, for the main protection circuit 112A to perform charger detection, a current path must be established between the charger and the main protection circuit 112A.

[0058] Figure 4 It shows Figure 1 The battery protection system 100 is shown, with the charger current detection path 400 highlighted. For clarity, details are omitted. Figure 1 Some of the reference numerals in the figures. It can be seen that because the current path via the disconnected secondary protection switches 110C and 110D is blocked, a current path is formed through the bypass circuit 118, via the battery 102, and into the ground pin 114D of the main protection circuit 112A.

[0059] Once the battery charger is connected, the main protection circuit 112A detects the presence of the charger and closes the main charging switch 110A (S302). The main discharging switch 110B remains open. Due to the body diode of the main discharging switch 110B, charging current can flow from the positive load / charging terminal 106A to the positive battery terminal 104A. Similarly, the secondary protection switches 110C and 110D do not change state, with the secondary charging switch 110C closed and the secondary discharging switch 110D open. The body diode of the secondary discharging switch 110D allows charging current to flow from the negative battery terminal 104B to the negative load / charging terminal 106B. Therefore, the battery charger can charge the battery 102 (S304). Figure 5 It shows Figure 1 and Figure 4 The battery protection system 100, in which the charging current path 500 is highlighted. For example... Figure 5 As shown, the charging current path 500 is in the form of a charging current loop.

[0060] Due to the voltage drop across the body diode of the secondary discharge switch 110D, the positive load / charge terminal 106A drops to a level above 2.25V, and the negative terminal drops to below zero volts.

[0061] Figure 6A battery protection system 1000 according to another embodiment of the present disclosure is shown. The battery protection system 1000 has a... Figure 1 The battery protection system 100 shares several common features with the battery protection system 100. However, the battery protection system 1000 includes several additional features, as will be explained below.

[0062] The battery protection system 1000 includes a single battery 1002, which in this embodiment is a rechargeable lithium-ion battery with a 5V rating. Battery 1002 is coupled to a positive battery terminal 1004A and a negative battery terminal 1004B. The battery protection system 1000 also includes a positive load / charge terminal 1006A and a negative load / charge terminal 1006B. Load / charge terminals 1006A and 1006B can be coupled to a load 1007; however, the load is not part of the battery protection system 1000.

[0063] Positive battery terminal 1004A is coupled to positive load / charge terminal 1006A via positive power rail 1008A. Negative battery terminal 1004B is coupled to negative load / charge terminal 1006B via negative power rail 1008B. The battery protection system 1000 also includes a pair of main protection switches, including a main charging switch 1010A and a main discharging switch 1010B. Additionally, a pair of secondary protection switches are provided along the negative power rail 1008B. The secondary protection switches include a secondary charging switch 1010C and a secondary discharging switch 1010D. The main and secondary protection switches can be MOSFETs or other suitable transistors or switches.

[0064] The battery protection system 1000 also includes a main protection circuit 1012A and a secondary protection circuit 1012B. The main protection circuit 1012A can be an integrated circuit (IC), such as the MAX17330 from Analog Devices, Wilmington, USA. The MAX17330 is a standalone battery charger and protector IC. The MAX17330 includes several features unrelated to this disclosure but usable in embodiments of the battery protection system 1000. Features relevant to this disclosure will be described below. The secondary protection circuit 1012B can be an IC, such as the S-82D1A from ABLIC, Tokyo, Japan. The S-82D1A is a battery protection IC.

[0065] The main protection circuit 1012A is coupled to main protection switches 1010A and 1010B. The secondary protection circuit 1012B is coupled to secondary protection switches 1010C and 1010D. The main protection circuit 1012A includes a charge control pin 1014A coupled to the main charge switch 1010A. The charge control pin provides charge FET control (CHG) in the MAX17330. The main protection circuit also includes a discharge control pin 1014B coupled to the main discharge switch 1010B. The discharge control pin 1014B provides discharge FET control (DIS) in the MAX17330.

[0066] The main protection circuit 1012A includes a battery sensing pin 1014C and a ground pin 1014D. In the MAX17330, the battery sensing pin 1014C is the battery connection (BATT), and the ground pin 1014D is the ground connection (GND). The battery sensing pin 1014C is connected to the positive battery terminal 1004A. The ground pin 1014D is connected to the negative battery terminal 1004B. The MAX17330 datasheet recommends coupling an external resistor and capacitor network to the battery and ground connections for effective operation. In this embodiment, the battery protection system 1000 includes a resistor R1 between the battery sensing pin 1014C and the positive battery terminal 1004A. The resistor can be 10Ω, although it can be 1Ω to 100Ω. Additionally, a capacitor C1, which can have a value of 0.1μF, is located in the bypass between the battery sensing pin 1014C and ground. C1 can be 0.01μF to 1μF. The main protection circuit 1012A takes into account R1 and C1 and can accurately sense the battery voltage. There are no active components located between the battery sensing pin 1014C and the battery, enabling accurate and constant sensing of the battery voltage.

[0067] The main protection circuit 1012A also includes a charger sensing pin 1014E coupled to the positive load / charging terminal 1006A. This is the battery pack positive terminal or system positive terminal (PCKP) in the MAX17330. In this embodiment, a current-limiting resistor R2 is located between the charger sensing pin 1014E and the positive load / charging terminal 1006A. R2 can have a value in the range of 100Ω to 10kΩ, although in this embodiment the value is 1kΩ.

[0068] The main protection circuit 1012A may also include a current sensing negative pin 1014F and a current sensing positive pin 1014G. These pins correspond to the CSN and CSP inputs in the MAX17330. These pins are connected across a current sensing resistor R3, which is arranged in series with the main protection switch along the positive power rail 1008A. These inputs enable the main protection circuit 1012A to measure the charging current, which can be helpful during charging mode. Since this aspect of the MAX17330 is not directly related to the operation of the battery protection system 1000 according to this disclosure, further details will not be provided here.

[0069] The main protection circuit 1012A also includes a thermistor connection pin 1014H. This is the TH pin in the MAX17330. This pin can be connected to a thermistor T2 used to sense the battery temperature. The thermistor can take values ​​from 10kΩ to 100kΩ, and in this case, it takes a value of 100kΩ.

[0070] The secondary protection circuit 1012B includes a charging control pin 1016A connected to the secondary charging switch 1010C and a discharging control pin 1016B connected to the secondary discharging switch 1010D. The charging control pin 1016A provides the charging control FET function (CO) of the S-82D1A. The discharging control pin 1016B provides the discharging control FET function (DO) of the S-82D1A.

[0071] The secondary protection circuit 1012B also includes a battery sensing pin 1016C and a ground pin 1016D. The battery sensing pin 1016C is the positive power supply (VDD) of the S-82D1A, and the ground pin 1016D is the negative power supply (VSS) of the S-82D1A. The battery sensing pin 1016C is connected to the positive battery terminal 1004A. The ground pin 1016D is connected to the negative battery terminal 1004B. Similar to the primary protection circuit 1012A, the secondary protection circuit 1012B may include a resistor R4 between the battery sensing pin 1016C and the positive battery terminal 1004A. A bypass capacitor C2 may be positioned between the battery sensing pin 1016C and ground. In one embodiment, R4 may be 330Ω, and C2 may be 0.1μF. The value of R4 may be in the range of 270Ω to 1.2kΩ. The value of capacitor C2 may be in the range of 0.068μF to 2.2μF. Considering the values ​​of R4 and C2, the secondary protection circuit 1012B can accurately sense the battery voltage. No active components are located between the battery sensing pin 1016C and the battery 1002, enabling accurate and constant sensing of the battery voltage.

[0072] The secondary protection circuit 1012B also includes a charger sensing pin 1016E, which is coupled to the negative load / charging terminal 1006B via resistor R5. This pin corresponds to the external negative connection (VM) in the S-82D1A. R5 can take values ​​ranging from 300Ω to 1.5kΩ, and in this embodiment, it can have a value of 470Ω. The primary function of the VM input in the S-82D1A is to provide electrostatic discharge (ESD) protection and protection against reverse charger connection. However, as mentioned above, this pin also provides an undervoltage protection current path for charger detection.

[0073] The secondary protection circuit 1012B also includes a thermistor connection pin 1016F. This is the TH pin in the S-82D1A. This pin can be connected to a thermistor T1 used to sense the battery temperature. The thermistor can take values ​​in the range of 10kΩ to 100kΩ, and in this case, it takes a value of 100kΩ.

[0074] The secondary protection circuit 1012B also includes an overcurrent detection pin (VINI) 1016G. The overcurrent detection resistor R6 is connected in series with the negative power rail 1008B and is located between the battery negative terminal 1004B and the secondary protection switches 1010C and 1010D. R6 can be 1.5mΩ and enables the secondary protection circuit 1012B to perform overcurrent detection.

[0075] The secondary protection circuit 1012B also includes a bypass circuit 1018. The bypass circuit 1018 provides a switchable current path between the battery sensing node 1016C and the charger sensing pin 1016E. The bypass circuit 1018 may be a switch and resistor (not shown) connected in series between the battery sensing pin 1016C and the charger sensing pin 1016E.

[0076] In an alternative embodiment, the bypass circuit may be located outside the secondary protection circuit. The bypass circuit may include a bypass resistor formed in series with a bypass switch. The bypass circuit may be coupled between the positive and negative power rails. The bypass circuit may be coupled to the positive power rail between the positive battery terminal and the main protection switch. The bypass circuit may be coupled to the negative power rail between the secondary protection switch and the negative load / charging terminal. The bypass switch may be a MOSFET and may be coupled to the secondary discharge pin. The bypass switch may close when the secondary discharge switch opens when the battery voltage drops below the secondary undervoltage threshold, thereby enabling a current path to be formed between the positive battery terminal and the negative load / charging terminal.

[0077] In a further embodiment, the secondary protection circuit 112B may not require the use of the bypass circuit 118, or the bypass circuit may be omitted entirely. As described above, when the battery voltage drops below the second undervoltage threshold, the battery protection system 100 operates to prevent leakage from the battery 102. This is achieved by disconnecting the secondary protection switch 110D. By doing so, charger detection is disabled. The bypass circuit 118 is used to form a current path between the main protection circuit 112A and the negative load / charger port 106B to enable charger detection in this situation. In some applications, the current leakage from the battery may be low enough that it is not necessary to disconnect the secondary protection switch 110D to prevent battery discharge. In this case, the current path between the main protection circuit 112A and the negative load / charger port 106B is maintained, and the bypass circuit is not required. This current path may be referred to as the main charger detection current path, and the battery protection system may be considered to be in a first mode; however, Figure 4 The current path 400 shown can be referred to as the secondary charger detection current path (including bypass circuitry), and the battery protection system can be considered to be in a second mode. This arrangement provides a simpler implementation of the parallel protection circuit topology when battery leakage is not a critical issue.

[0078] Battery protection systems can be particularly useful in smaller electronic devices, such as oral care devices (e.g., electric toothbrushes). Alternatively, they can also be used in other electronic appliances, including floor care appliances (e.g., stick vacuum cleaners) or hair care appliances (e.g., hair dryers).

[0079] An electronic appliance may include: a battery charger docking station configured to receive a battery charger. The docking station may be coupled to a load / charging port. The docking station may be wireless or wired. The appliance may include a load coupled to the load / charging port. The load may be an electric motor. The appliance may also include a user interface coupled to a battery protection system and configured to control the discharge of the battery to the load. For example, the user interface may include an on / off switch configured to turn the motor on and off.

Claims

1. A battery protection system, comprising: Battery; The load / charging port is configured to be coupled to a load or battery charger. The main protection switch is coupled between the battery and the load / charging port; The secondary protection switch is coupled between the battery and the load / charging port; The main protection circuit is configured to sense the voltage across the battery and control the main protection switch based on the sensed voltage. and The secondary protection circuit is configured to sense the voltage across the battery and control the secondary protection switch based on the sensed voltage. The main protection circuit and the secondary protection circuit are arranged in parallel across the battery.

2. The battery protection system according to claim 1, wherein, The main protection circuit is coupled across the battery between the battery and the main protection switch and the secondary protection switch.

3. The battery protection system according to claim 2, wherein, The main protection circuit is also configured to detect the presence of a battery charger coupled to the load / charging port.

4. The battery protection system according to claim 3, wherein, The main protection circuit includes a main ground connection coupled to the negative terminal of the battery.

5. The battery protection system according to claim 4, wherein, The main protection circuit includes a battery voltage sensing connection coupled to the positive terminal of the battery, and is also configured to sense the battery voltage via the battery voltage sensing connection and the main ground connection.

6. The battery protection system according to claim 5, wherein, The main protection circuit includes a battery charger detection connection coupled to the load / charging port, and is also configured to detect the battery charger via the battery charger detection connection and the main ground connection.

7. The battery protection system according to any one of claims 4 to 6, wherein, The secondary protection circuit includes a secondary ground connection, wherein the primary ground connection and the secondary ground connection are coupled to the negative terminal of the battery.

8. The battery protection system according to any one of the preceding claims, wherein, The main protection switch is coupled between the first terminal of the battery and the first terminal of the load / charge port, and the secondary protection switch is coupled between the second terminal of the battery and the second terminal of the load / charge port.

9. The battery protection system according to claim 8, wherein, The first terminal is the positive terminal, and the second terminal is the negative terminal.

10. The battery protection system according to any one of the preceding claims, wherein, The main protection circuit is the first integrated circuit, and the secondary protection circuit is the second integrated circuit.

11. The battery protection system according to any one of the preceding claims, wherein, The main protection circuit is also configured to disconnect the main protection switch when the battery voltage drops below a first threshold voltage.

12. The battery protection system according to claim 11, wherein, The secondary protection circuit is also configured to disconnect the secondary protection switch when the battery voltage drops below the second threshold voltage.

13. The battery protection system according to claim 12, wherein, The second threshold voltage is less than the first threshold voltage.

14. The battery protection system according to any one of the preceding claims, wherein, The main protection circuit is also configured to detect the presence of a battery charger coupled to the load / charging port and to control the main protection switch at least in part based on the presence of the battery charger.

15. The battery protection system according to claim 14, further comprising: The bypass circuit is coupled between the battery and the load / charging port.

16. The battery protection system according to claim 15, wherein: In the first mode, the secondary protection switch is closed, and the main protection circuit is also configured to detect the presence of the battery charger via the main charger detection current path including the secondary protection switch. and In the second mode, the secondary protection switch is open, and the main protection circuit is also configured to detect the presence of the battery charger via a secondary charger detection current path that includes a bypass circuit.

17. The battery protection system according to claim 16, wherein, The bypass circuit includes at least one bypass resistor and at least one bypass switch, and in the second mode of operation, the at least one bypass switch is closed.

18. The battery protection system according to claim 17, wherein, The second mode of operation is the undervoltage operation mode when the battery voltage drops below the undervoltage threshold.

19. The battery protection system according to any one of claims 15 to 18, wherein, The bypass circuit is coupled between the positive terminal of the battery and the negative terminal of the load / charge port.

20. The battery protection system according to any one of claims 15 to 19, wherein, The secondary protection circuit includes a bypass circuit.

21. The battery protection system according to any one of claims 16 to 20, wherein, The current detection path for the secondary charger also includes the battery.

22. The battery protection system according to any one of claims 14 to 21, wherein, The main protection circuit is also configured to close the main protection switch when a battery charger is detected, so as to allow the battery charger to charge the battery.

23. The battery protection system according to claim 22, wherein, The system is configured to form a charging current loop via a main protection switch and a secondary protection switch during charging, and to allow current to flow through the body diode of the secondary protection switch when the secondary protection switch is open.

24. A method of operating a battery protection system according to any one of claims 1 to 23, comprising: Use the main protection circuit to sense the voltage across the battery; Use secondary protection circuitry to sense the voltage across the battery; Based on the voltage sensed by the main protection circuit, the main protection circuit is used to control the main protection switch; and The secondary protection circuit controls the secondary protection switch based on the voltage sensed by the secondary protection circuit.

25. The method of claim 24, further comprising: When the battery voltage drops below the first threshold voltage, the main protection circuit disconnects the main protection switch.

26. The method of claim 25, further comprising: When the battery voltage drops below the second threshold voltage, the secondary protection circuit disconnects the secondary protection switch.

27. The method according to claim 26, wherein, The second threshold voltage is less than the first threshold voltage.

28. The method according to any one of claims 24 to 27, further comprising: When the secondary protection switch is closed, the presence of the battery charger is detected by the main protection circuit via the main charger detection current path, which includes the secondary protection switch. and Close the main protection switch to allow the battery to be charged.

29. The method of claim 24, further comprising, when subordinate to claim 15: When the secondary protection switch is off, the presence of the battery charger is detected by the main protection circuit via the secondary charger detection current path, which includes the bypass circuit. and Close the main protection switch to allow the battery to be charged.

30. An electronic appliance comprising a battery protection system according to any one of claims 1 to 23.

31. The electronic appliance according to claim 30, further comprising: A battery charger docking station is configured to receive a battery charger and couple to a load / charging port. The load is coupled to the load / charging port; and The user interface is coupled to the battery protection system and configured to control the discharge of the battery to the load.

32. The electronic appliance according to claim 31, wherein, The load is an electric motor.

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