Battery secondary protection circuit and operation method thereof

Abstract

The present invention provides a battery secondary protection circuit and an operating method thereof, wherein the battery secondary protection circuit comprises a first pin, a second pin, a first sensing circuit, a first current source, a first enabling circuit and a first protection circuit. The first pin and the second pin are respectively coupled to two ends of a first battery. The first sensing circuit is coupled between the first pin and the second pin, and provides a first sensing signal and a second sensing signal. The first current source is coupled between the first pin and the second pin and provides a first current. The first enabling circuit couples the first sensing circuit and the first current source, and generates a first enabling signal according to the first sensing signal. The first protection circuit is coupled to the first sensing circuit. When the first enabling signal enables the first current source, the first protection circuit generates a first protection signal according to the second sensing signal changed by the first current. The battery secondary protection circuit and the operating method thereof of the present invention can significantly reduce unnecessary power consumption, achieve energy saving and power saving effects while providing overvoltage and open line protection functions at the same time.

Description

Technical Field

[0001] The present invention relates to a battery secondary protection circuit, and in particular to a battery secondary protection circuit and an operation method thereof. Background Art

[0002] Please refer to Figure 1 Generally speaking, when batteries B1 and B2 are working normally, the primary protection circuit IC1 and the secondary protection circuit IC2 monitor the status of batteries B1 and B2 at the same time. The primary protection circuit IC1 achieves repetitive protection actions by controlling the protection switch M1 / M2 to turn on / off the charging path. When the primary protection circuit IC1 fails, the secondary protection circuit IC2 executes the protection mechanism. When the secondary protection circuit IC2 detects an over-voltage event, it will send a protection signal PT to melt the fuse FS set on the power supply path, thereby providing a one-time over-voltage protection (Over-Voltage Protection, OVP). In order to continuously monitor the battery status, the existing battery protection circuit usually needs to continuously sense the cross-voltage of each battery.

[0003] In addition, for portable devices powered by lithium batteries (such as electric drills and other tools that generate vibrations), during operation, the welding points of the battery protection circuit may fall off due to vibrations, causing the battery protection circuit to be unable to sense the battery status, so it is also necessary to provide an open-wire protection (OWP) function for this situation. In the prior art, only one protection circuit provides an open-wire protection function. When the primary protection circuit fails, the open-wire protection mechanism is lost.

[0004] However, if both overvoltage protection and open-line protection are added to all protection circuits at the same time, the open-line protection circuit needs to be equipped with an additional high-power consumption circuit (such as a current source and / or a large resistor coupled to the working voltage), and its power consumption is about 2 to 3 times that of the overvoltage protection circuit. In addition, when the protection circuit is in continuous operation, it is bound to cause a significant increase in the power consumption of the product. The above shortcomings need to be overcome urgently. Summary of the invention

[0005] In view of this, the present invention proposes a battery secondary protection circuit and an operation method thereof to effectively solve the above problems encountered in the prior art.

[0006] According to a specific embodiment of the present invention, a secondary protection circuit for a battery is provided. In this embodiment, the secondary protection circuit for the battery includes a first pin, a second pin, a first sensing circuit, a first current source, a first enabling circuit and a first protection circuit. The first pin and the second pin are respectively coupled to the two ends of the first battery. The first sensing circuit is coupled between the first pin and the second pin, and provides a first sensing signal and a second sensing signal. The first current source is coupled between the first pin and the second pin and provides a first current. The first enabling circuit couples the first sensing circuit and the first current source, and generates a first enabling signal according to the first sensing signal. The first protection circuit is coupled to the first sensing circuit. When the first enabling signal enables the first current source, the first protection circuit generates a first protection signal according to the second sensing signal changed by the first current.

[0007] In one embodiment, the first protection circuit includes a first comparator. The first comparator provides an open-line protection signal according to a comparison result between the second sensing signal and the first threshold.

[0008] In one embodiment, the first protection circuit includes a second comparator. The second comparator provides an overvoltage protection signal according to a comparison result between the third sensing signal provided by the first sensing circuit and the second threshold.

[0009] In one embodiment, the battery secondary protection circuit further includes a third pin, a second sensing circuit, a second enabling circuit and a second protection circuit. The second pin and the third pin are respectively coupled to two ends of the second battery. The second sensing circuit is coupled between the second pin and the third pin, and provides a fourth sensing signal and a fifth sensing signal according to the second voltage and the third voltage on the third pin. The second enabling circuit is coupled to the second sensing circuit, and generates a second enabling signal when the fourth sensing signal is greater than the fifth threshold value. The second protection circuit is coupled to the second sensing circuit, and generates a second protection signal according to the fourth sensing signal when the second current source is enabled.

[0010] In one embodiment, the secondary battery protection circuit further includes a logic circuit, which is respectively coupled to the first enabling circuit and the second enabling circuit, and sends an enabling signal to enable the first current source when receiving at least one of the first enabling signal and the second enabling signal.

[0011] In one embodiment, the battery secondary protection circuit further includes a second current source coupled between the second pin and the third pin. The second current provided by the second current source is not equal to the first current. Either the first enable signal or the second enable signal enables the first current source and the second current source simultaneously.

[0012] In one embodiment, the first sensing signal and the second sensing signal have the same voltage value.

[0013] In one embodiment, the first sensing signal and the second sensing signal have different voltage values.

[0014] In one embodiment, the first current is a pulse signal with an adjustable duty cycle.

[0015] Another specific embodiment of the present invention is an operating method of a secondary battery protection circuit. In this embodiment, the operating method is applied to the secondary battery protection circuit. The secondary battery protection circuit includes a first pin and a second pin, which are respectively coupled to two ends of a first battery. A first current source is coupled between the first pin and the second pin and provides a first current. The operating method includes the following steps: (a) providing a first sensing signal and a second sensing signal respectively; (b) generating a first enabling signal according to the first sensing signal; and (c) when enabling the first current in response to the first enabling signal, generating a first protection signal according to the second sensing signal changed by the first current.

[0016] Compared to the prior art, the battery secondary protection circuit and its operating method of the present invention will only activate the battery protection function (such as open line protection and / or overvoltage protection) when the cross-voltage of at least one battery reaches a preset threshold (such as the open line protection sensing adopts the lower limit threshold / overvoltage protection sensing adopts the upper limit threshold), thereby greatly reducing unnecessary power consumption, so as to achieve energy saving and power saving while providing overvoltage and open line protection functions at the same time, and is particularly suitable for portable devices powered by lithium batteries (such as electric drills and other tools that generate vibrations).

[0017] The advantages and spirit of the present invention can be further understood through the following detailed description of the invention and the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is an architecture diagram of the existing battery protection system.

[0019] Figure 2 FIG. 4 is a schematic diagram of a secondary battery protection circuit in an embodiment of the present invention.

[0020] Figure 3 It is a schematic diagram of a battery secondary protection circuit in another embodiment of the present invention.

[0021] Figure 4A and Figure 4B They are different embodiments of a sensing circuit, an enabling circuit and a protection circuit in a secondary battery protection circuit.

[0022] Figure 5 The invention is an embodiment of a first current source in a secondary protection circuit of a battery.

[0023] Figure 6 for Figure 4B Waveform timing diagram of the battery secondary protection circuit.

[0024] Fig. 7A and Figure 7B The waveform timing diagram of open-line sensing and overvoltage sensing for the battery secondary protection circuit.

[0025] Figure 8 FIG. 4 is a flow chart of a battery operation method according to another embodiment of the present invention.

[0026] Description of main component symbols:

[0027] IC1 primary protection circuit

[0028] IC2 Secondary protection circuit

[0029] FS Fuse

[0030] M1, M2 protection switch

[0031] DO, CO pins

[0032] SC1, SC2 sensing circuit

[0033] PC1, PC2 protection circuit

[0034] OVP1, OVP2 overvoltage protection signal

[0035] OR Gate

[0036] P+ High voltage terminal

[0037] P- low voltage terminal

[0038] 1. 1' Battery secondary protection circuit

[0039] 101, 111, 121, 131 sensing circuit

[0040] 102, 112, 122, 132 protection circuit

[0041] 113, 123, 133 enabling circuit

[0042] 114, 124, 134 Current Source

[0043] 14, 15 Logic Circuit

[0044] B1~B3 Batteries

[0045] P0~P4 pins

[0046] VC1~VC4 First voltage~fourth voltage

[0047] VDD Operating Voltage

[0048] EN Enable signal

[0049] PT protection signal

[0050] VS0~VS9 sensing signal

[0051] PT0~PT3 protection signal

[0052] EN1~EN3 enable signal

[0053] Nodes N1 to N4

[0054] VN1~VN4 node voltage

[0055] I1~I3 Current

[0056] R1~R4 resistors

[0057] V12, V23, V34 voltage division

[0058] TH1~TH3 threshold

[0059] OWP open line protection signal

[0060] OVP overvoltage protection signal

[0061] 1120 Comparator

[0062] 1121 Comparator

[0063] 1122 OR Gate

[0064] 1130 Comparator

[0065] 1140 Clock Generation Circuit

[0066] 1142 Current generating circuit

[0067] CLK Clock signal

[0068] VSEN voltage divider

[0069] t0~t3 time

[0070] VC1-VC2 Voltage difference between pin P1 and pin P2

[0071] Steps S10 to S14 DETAILED DESCRIPTION

[0072] Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Elements / components using the same or similar reference numerals in the drawings and embodiments are intended to represent the same or similar parts.

[0073] A preferred embodiment of the present invention is a secondary battery protection circuit. In this embodiment, the secondary battery protection circuit can be connected in series with the primary battery protection circuit and the fuse to provide a one-time overvoltage protection for the battery. However, this is not limited to this.

[0074] Please refer to Figure 2 The battery secondary protection circuit 1 includes a power pin P0, pins P1-P4, current sources 114, 124, 134, sensing circuits 101, 111, 121, 131, protection circuits 102, 112, 122, 132, enabling circuits 113, 123, 133 and logic circuits 14, 15.

[0075] Pins P1 and P2 are coupled to two ends of battery B1, respectively. Pins P2 and P3 are coupled to two ends of battery B2, respectively. Pins P3 and P4 are coupled to two ends of battery B3, respectively. Current source 114 is coupled between pins P1 and P2. Current source 124 is coupled between pins P2 and P3. Current source 134 is coupled between pins P3 and P4.

[0076] The sensing circuit 101 is coupled between the power pin P0 and the pin P1. The sensing circuit 111 is coupled between the pin P1 and the pin P2. The sensing circuit 121 is coupled between the pin P2 and the pin P3. The sensing circuit 131 is coupled between the pin P3 and the pin P4.

[0077] The protection circuit 102 is coupled between the sensing circuit 101 and the logic circuit 14. The protection circuit 112 is coupled between the sensing circuit 111 and the logic circuit 14. The protection circuit 122 is coupled between the sensing circuit 121 and the logic circuit 14. The protection circuit 132 is coupled between the sensing circuit 131 and the logic circuit 14.

[0078] The enabling circuit 113 is coupled between the sensing circuit 111 and the logic circuit 15. The enabling circuit 123 is coupled between the sensing circuit 121 and the logic circuit 15. The enabling circuit 133 is coupled between the sensing circuit 131 and the logic circuit 15.

[0079] The sensing circuit 111 generates a sensing signal VS1 to the enabling circuit 113 and a sensing signal VS2 to the protection circuit 112 according to the voltage VC1 on the pin P1 and the voltage VC2 on the pin P2 coupled to the two ends of the battery B1. The enabling circuit 113 selectively generates an enabling signal EN1 to the logic circuit 15 according to the sensing signal VS1.

[0080] Similarly, the sensing circuit 121 and the sensing circuit 131 respectively generate sensing signals VS3 and VS5 to the enabling circuits 123 and 133 according to the voltages VC2, VC3 and VC4 on the pins P2, P3 and P4 coupled to the two ends of the battery B2 and the battery B3, and generate sensing signals VS4 and VS6 to the protection circuits 122 and 132. The enabling circuits 132 and 133 selectively generate enabling signals EN2 and EN3 to the logic circuit 15 according to the sensing signal VS3.

[0081] When the logic circuit 15 receives at least one of the enable signals EN1-EN3, the logic circuit 15 will send out the enable signal EN to respectively enable the current sources 114, 124, 134, so that the current sources 114, 124, 134 generate currents I1, I2, I3 respectively. In other words, once the logic circuit 15 receives one or more enable signals, the logic circuit 15 will enable all the current sources in the battery secondary protection circuit 1 to generate currents respectively, but not limited to this. In practical applications, the currents I1, I2, I3 generated by the current sources 114, 124, 134 can be pulse current signals with adjustable duty cycles to further reduce energy consumption, but not limited to this. For example, if the currents I1, I2, I3 are all pulse current signals with a duty cycle of 50%, the total power consumption of the protection circuit is approximately 50% of the continuous current of the currents I1, I2, I3.

[0082] If a disconnection (opening) occurs between the battery B1 and the pin P1 or the pin P2, when the enable signal EN enables the current source 114, the protection circuit 112 generates a protection signal PT1 to the logic circuit 14 according to the sensing signal VS2 changed by the current source 114. Similarly, when a disconnection (opening) occurs between the battery B2 and the pin P2 or the pin P3, when the enable signal EN enables the current source 124, the protection circuit 122 generates a protection signal PT2 to the logic circuit 14 according to the sensing signal VS4 changed by the current source 124. The same is true for a disconnection (opening) between the battery B3 and the pin P3 or the pin P4, which will not be described in detail here.

[0083] In addition, the sensing circuit 101 provides a sensing signal VS0 to the protection circuit 102 according to the working voltage VDD on the power pin P0 and the first voltage VC1 on the first pin P1. The protection circuit 102 selectively generates a protection signal PT0 to the logic circuit 14 according to the sensing signal VS0.

[0084] When the logic circuit 14 receives at least one of the protection signals PT0-PT3, the logic circuit 14 will issue a protection signal PT to start the circuit protection operation. In other words, once the logic circuit 14 receives one or more protection signals, the logic circuit 14 will start the circuit protection operation, such as a one-time protection of blowing a fuse, but not limited thereto.

[0085] It should be noted that the current I2 generated by the current source 124 is not equal to the currents I1 and I3 generated by the adjacent current sources 114 and 134, so as to generate a current difference between the pin P2 (node ​​N2) and the pin P3 (node ​​N3), thereby achieving the effect of open-line sensing. Figure 2 The current I2 (eg, 0.1 uA) generated by the current source 124 is not equal to the currents I1 (eg, 1 uA) and I3 (eg, 1 uA) generated by the current sources 114 and 134 , but the present invention is not limited thereto.

[0086] In another embodiment, if Figure 3 As shown, the battery secondary protection circuit 1 ′ may not set any current source between the pin P2 and the pin P3 , so a current difference of current values ​​I2 and I3 is generated at the pin P2 and the pin P3 respectively, but the present invention is not limited thereto.

[0087] Next, please refer to Figure 4A and Figure 4B . Figure 4A and Figure 4B They are different embodiments of a sensing circuit, an enabling circuit and a protection circuit in a secondary battery protection circuit.

[0088] In one embodiment, if Figure 4A As shown, if the sensing circuit 111, the protection circuit 112 and the enabling circuit 113 in the secondary battery protection circuit 1 are used as an example for explanation, the sensing circuit 111 includes resistors R1-R4 connected in series. The resistors R1-R4 are connected in parallel with the current source 114. The protection circuit 112 includes a comparator 1120, a comparator 1121 and an OR gate 1122. The enabling circuit 113 includes a comparator 1130.

[0089] The resistors R1 - R4 are used for dividing the voltage VC1 on the first pin P1 and the voltage VC2 on the second pin P2 to generate divided voltages V12 , V23 and V34 respectively.

[0090] An input terminal of the comparator 1130 in the enabling circuit 113 receives the threshold value TH3 and another input terminal thereof is coupled between the resistors R2 and R3 to receive the divided voltage V23 (ie Figure 2 The comparator 1130 generates a sense signal VS1 according to the divided voltage V23 (i.e. Figure 2 The comparison result of the sensing signal VS1 in the output signal VS1 and the threshold TH3 is used to generate an enable signal EN1.

[0091] An input terminal of the comparator 1120 receives the threshold TH1 and another input terminal thereof is coupled between the resistors R1 and R2 to receive the divided voltage V12 (ie Figure 2The comparator 1120 and the comparator 1121 are connected to the input terminal of the OR gate 1122. The comparator 1120 and the comparator 1121 are connected to the input terminal of the OR gate 1122.

[0092] When the current source 114 is enabled, the current source 114 starts to draw / sink current from the pins P1 and P2. Figure 2 If the battery B1 is normally connected to the pins P1 and P2, the current I1 generated by the current source 114 will be balanced by the charge stored in the battery B1 and will not affect the voltages of the nodes N1 and N2. When the battery B1 is abnormally connected to the pins P1 and P2, the current I1 generated by the current source 114 will cause the divided voltage V23 (i.e. Figure 2 The sensing signal VS1 in the comparator 1120 and the divided voltage V12 (i.e. Figure 2 The comparator 1120 changes according to the divided voltage V12 (i.e. Figure 2 The comparison result of the sensing signal VS2 in the voltage divider V34 and the threshold TH1 provides an open line protection signal OWP to the OR gate 1122. The comparator 1121 provides an overvoltage protection signal OVP to the OR gate 1122 according to the comparison result of the divided voltage V34 and the threshold TH2. The OR gate 1122 issues a protection signal PT1 according to the open line protection signal OWP and / or the overvoltage protection signal OVP.

[0093] It should be noted that the threshold TH1 received by the comparator 1120, the threshold TH2 received by the comparator 1121 and the threshold TH3 received by the comparator 1130 may be equal to each other, that is, the comparator 1120 and the comparator 1121 of the protection circuit 112 and the comparator 1130 of the enabling circuit 113 may share the same threshold, but is not limited to this.

[0094] For example, the thresholds TH1 ˜ TH3 are all 2V, the current I1 generated by the current source 114 is 1uA, and the resistance values ​​of the resistors R1 ˜ R4 are 0.2MΩ, 0.8MΩ, 0.05MΩ, and 0.95MΩ, respectively, but the present invention is not limited thereto.

[0095] In another embodiment, if Figure 4B As shown, the sensing circuit 111 includes resistors R1-R2 connected in series. The resistors R1-R2 are connected in parallel with the current source 114. The protection circuit 112 includes a comparator 1120, a comparator 1121 and an OR gate 1122. The enabling circuit 113 includes a comparator 1130.

[0096] The resistors R1-R2 are used to divide the voltages VC1 and VC2 to generate a divided voltage VSEN between the resistors R1 and R2. An input terminal of the comparator 1130 receives the threshold TH3 and another input terminal thereof is coupled between the resistors R1 and R2 to receive the divided voltage VSEN. The comparator 1130 generates a voltage VSEN according to the divided voltage VSEN (i.e. Figure 2 The comparison result of the sensing signal VS2 in the output and the threshold TH3 is used to generate an enabling signal EN1.

[0097] An input terminal of the comparator 1120 receives the threshold value TH1 and another input terminal thereof is coupled between the resistors R1 and R2 to receive the divided voltage VSEN. An input terminal of the comparator 1121 receives the threshold value TH2 and another input terminal thereof is coupled between the resistors R1 and R2 to receive the divided voltage VSEN. The output terminals of the comparator 1120 and the comparator 1121 are both coupled to the input terminal of the OR gate 1122.

[0098] In other words, the comparator 1120 and the comparator 1121 of the protection circuit 112 and the comparator 1130 of the enabling circuit 113 can share the same divided voltage VSEN (ie Figure 2 The voltage values ​​of the sensing signals VS1 and VS2 are equal, both are divided voltages VSEN), but this is not limited to this.

[0099] In one embodiment, the voltage difference between pin P1 and pin P2 (i.e., VC1-VC2) is 4V, the resistance values ​​of resistors R1 and R2 are both 2MΩ, the current I1 generated by the current source 114 is 1uA, the threshold TH1=1.25V, the threshold TH2=2.35V, and the threshold TH3=2V, but is not limited to this.

[0100] When the current source 114 is enabled, the current source 114 starts to draw / sink current from the pins P1 and P2. Figure 2 If the battery B1 is normally connected to the pins P1 and P2, the current I1 generated by the current source 114 will be balanced by the charge stored in the battery B1 and will not affect the voltages of the nodes N1 and N2. If the battery B1 is abnormally connected to the pins P1 and P2, the current I1 generated by the current source 114 will cause the divided voltage VSEN received by the comparator 1130, the comparator 1120 and the comparator 1121 to change. The comparator 1120 changes the divided voltage VSEN (i.e. Figure 2 The comparison result of the sensing signal VS2 in the input voltage VSEN and the threshold TH1 provides an open line protection signal OWP to the OR gate 1122. The comparator 1121 provides an overvoltage protection signal OVP to the OR gate 1122 according to the comparison result of the divided voltage VSEN and the threshold TH2. The OR gate 1122 issues a protection signal PT1 according to the open line protection signal OWP and / or the overvoltage protection signal OVP.

[0101] In other words, once the OR gate 1122 receives the open line protection signal OWP first, the OR gate 1122 will issue the protection signal PT1. Once the OR gate 1122 receives the overvoltage protection signal OVP first, the OR gate 1122 will issue the protection signal PT1. Once the OR gate 1122 receives both the open line protection signal OWP and the overvoltage protection signal OVP, the OR gate 1122 will issue the protection signal PT1.

[0102] It should be noted that, although the above embodiment is described with reference to the sensing circuit 111, the protection circuit 112 and the enabling circuit 113 in the secondary battery protection circuit 1, in fact, the sensing circuit 121, the protection circuit 122 and the enabling circuit 123, as well as the sensing circuit 131, the protection circuit 132 and the enabling circuit 133 in the secondary battery protection circuit 1 can also be deduced in the same manner, and will not be further elaborated herein.

[0103] In one embodiment, if Figure 5 As shown, the current source 114 may include a clock generating circuit 1140 and a current generating circuit 1142. The clock generating circuit 1140 is coupled to the current generating circuit 1142. When the clock generating circuit 1140 receives the enable signal EN, the clock generating circuit 1140 is enabled to generate a clock signal CLK to the current generating circuit 1142 to control the current generating circuit 1142 to generate the current I1, and the clock signal CLK may be, for example, a pulse current signal with an adjustable duty cycle, but is not limited thereto. For example, if the current I1 is a pulse current signal with a duty cycle of 50%, its power consumption is approximately 50% of that of the current I1 being a continuous current signal.

[0104] Please refer to Figure 6 , Figure 6 for Figure 4B The waveform timing diagram of the battery secondary protection circuit in FIG. Assuming that the resistance values ​​of resistors R1 and R2 are equal, the voltage divider VSEN (i.e. Figure 2 The sensing signals VS1 and VS2 in FIG. 1 are half of the voltage difference (VC1-VC2) between the pins P1 and P2.

[0105] At time t1, when the voltage difference (VC1-VC2) between pins P1 and P2 exceeds 4V (i.e., the voltage division VSEN exceeds the threshold TH3=2V), the enable signal EN1 issued by the enable circuit 113 changes from the original low level to the high level, so that the enable signal EN issued by the logic circuit 15 also changes from the original low level to the high level, so as to enable the current source 114 to generate the current I1 and start the open line protection operation. In actual applications, the current I1 generated by the current source 114 can be a pulse current signal with an adjustable duty cycle, such as Figure 6 The current I1 during the time period from t1 to t3 is a pulse signal, but the present invention is not limited thereto.

[0106] At time t2, when the voltage difference (VC1-VC2) between pin P1 and pin P2 exceeds the safety value 4.7V (that is, the divided voltage VSEN exceeds the threshold TH2=2.35V), the comparator 1121 will send an overvoltage protection signal OVP to the OR gate 1122, and then the OR gate 1122 will send a protection signal PT1 to the logic circuit 14, so that the logic circuit 14 sends a protection signal PT to blow the fuse.

[0107] On the contrary, if the voltage difference (VC1-VC2) between the pins P1 and P2 does not exceed the safety value 4.7V (i.e., the divided voltage VSEN does not exceed the threshold TH2=2.35V), the comparator 1121 will not send the overvoltage protection signal OVP to the OR gate 1122. At this time, although the logic circuit 14 will not send the protection signal PT, the enable signal EN will still be maintained at a high level, i.e., the current source 114 will still be enabled to generate the current I1.

[0108] At time t3, when the voltage difference (VC1-VC2) between pins P1 and P2 is lower than 3.8V (ie, the divided voltage VSEN is lower than the threshold TH1=1.9V), the enable signal EN changes from a high level to a low level to disable the current source 114 from generating the current I1, ie, stops the open line protection action.

[0109] From the above, it can be seen that since the battery may explode due to overcharge only during charging, the enabling condition of the current source 114 is set during the period when the voltage difference (VC1-VC2) between the pins P1 and P2 increases, so as to achieve the purpose of reducing power consumption.

[0110] In addition, the comparator 1130 of the enabling circuit 113 has a voltage window. When the voltage difference (VC1-VC2) between the pin P1 and the pin P2 rises to 4V at time t1, the voltage VSEN between the resistors R1 and R2 is 2V, and the enabling signal EN becomes a high level; when the voltage difference (VC1-VC2) between the pin P1 and the pin P2 decreases to 3.8V at time t3, the voltage VSEN between the resistors R1 and R2 is 1.9V, and the enabling signal EN becomes a low level. Therefore, only during the period from time t1 to t3, the current source 114 will be enabled to generate the current I1. As for the comparators 1120 and 1121 and the OR gate 1122 in the protection circuit 112, they are all in a state of continuous operation.

[0111] It should be noted that the above embodiment is described by taking the pins P1 and P2 coupling the two ends of the battery B1 as an example. If it is extended to multiple batteries connected in series (for example Figure 1In the case of batteries B1~B3 in the circuit, the voltage across each battery (e.g., batteries B1~B3) (also the voltage difference between the two pins coupling each battery) must be reduced to below 3.8V, so that the enable signal EN1~EN3 corresponding to each battery becomes a low level. At this time, the enable signal EN will change from a high level to a low level to disable the current source 114 and stop generating the current I1, i.e., stop the open line protection action.

[0112] Please refer to Fig. 7A and Figure 7B , Fig. 7A and Figure 7B The waveform timing diagram of open-line sensing and overvoltage sensing for the battery secondary protection circuit.

[0113] like Fig. 7A As shown, assuming Figure 2 The soldering point between the pin P1 and the battery B1 is broken off. At time t0, the batteries B1-B3 are coupled to the working voltage VDD and start charging. The sensing circuits 111, 121, and 131 are connected in series, so that the voltage difference between the nodes N1 and N2, the voltage difference between the nodes N2 and N3, and the voltage difference between the nodes N3 and N4 are all 4V. If the node voltage VN4 of the node N4 is 0V, the node voltage VN1 of the node N1, the node voltage VN2 of the node N2, and the node voltage VN3 of the node N3 are 12V, 8V, and 4V, respectively.

[0114] During the period from time t0 to t1, the node voltages VN1-VN3 of the nodes N1-N3 will rise linearly in response to the charging current. Since the sensing circuits 111, 121, 131 formed by the voltage divider resistors are connected in series between the nodes N1-N4, even if the pin P1 is disconnected (not conducting with the battery B1), the node voltage VN1 of the node N1 will still rise linearly like the node voltages VN2-VN3 of the other nodes N2-N3 due to the voltage division.

[0115] At time t1, when at least one of the node voltages VN1-VN3 of the nodes N1-N3 rises to its corresponding threshold voltages 12V, 8V and 4V (ie Figure 4B When the voltage VSEN in the circuit is 2V), the enable signal EN changes from low level to high level to enable the current source 114. At this time, the current source 114 draws 1.5uA of current from the node N1, but the node N1 cannot be supplied with power by the battery B1 because the pin P1 is off, causing the node voltage VN1 there to drop from 12V.

[0116] At time t2, when the node voltage VN1 of the node N1 drops to 10.5V (i.e., the threshold TH1), the comparator 1120 in the protection circuit 112 will send an open line protection signal OWP to the OR gate 1122, and the OR gate 1122 will send a protection signal PT1 to the logic circuit 14 according to the open line protection signal OWP, and the logic circuit 14 will then send a protection signal PT to start the operation of the open line protection mechanism.

[0117] In other words, the threshold TH1 used for open line protection sensing is a lower limit voltage value. As long as the node voltage of a certain node (for example, the node voltage VN1 of the node N1) drops to its corresponding threshold TH1, it means that an open line event occurs in the circuit, so the open line protection signal OWP is immediately issued to activate the protection mechanism.

[0118] like Figure 7B As shown, assuming Figure 2 The soldering point between the pin P2 and the battery B1 is broken off. At time t0, the batteries B1-B3 are coupled to the working voltage VDD and start charging. The sensing circuits 111, 121, and 131 are connected in series, so that the voltage difference between the nodes N1 and N2, the voltage difference between the nodes N2 and N3, and the voltage difference between the nodes N3 and N4 are all 4V. If the node voltage VN4 of the node N4 is 0V, the node voltage VN1 of the node N1, the node voltage VN2 of the node N2, and the node voltage VN3 of the node N3 are 12V, 8V, and 4V, respectively.

[0119] During the period from time t0 to t1, the node voltages VN1-VN3 of the nodes N1-N3 will rise linearly in response to the charging current. Since the sensing circuits 111, 121, 131 formed by the voltage divider resistors are connected in series between the nodes N1-N4, even if the pin P2 is disconnected (not conducting with the batteries B1-B2), the node voltage VN2 of the node N2 will still rise linearly like the node voltages VN1, VN3 of the other nodes N1, N3 due to the voltage division.

[0120] At time t1, when at least one of the node voltages VN1-VN3 of the nodes N1-N3 rises to its corresponding threshold voltages 12V, 8V and 4V (ie Figure 4B When the divided voltage VSEN in the circuit is 2V), the enable signal EN changes from a low level to a high level to enable the current source 114. Figure 2 The current source 114 will inject 1.5uA of current into the node N2 and the current source 124 will draw 0.5uA of current from the node N2. However, the node N2 cannot discharge the net current of 1uA through the batteries B1 and B2 because the pin P2 is off, causing the node voltage VN2 of the node N2 to rise from 8V.

[0121] At time t3, when the node voltage VN2 of the node N2 rises to 8.7V (i.e., the threshold TH2), the comparator 1121 in the protection circuit 112 sends an overvoltage protection signal OVP to the OR gate 1122. The OR gate 1122 sends a protection signal PT1 to the logic circuit 14 according to the overvoltage protection signal OVP. The logic circuit 14 then sends a protection signal PT to activate the protection mechanism.

[0122] In other words, the threshold TH2 used for overvoltage protection sensing is the upper limit voltage value. As long as the node voltage of a certain node (for example, the node voltage VN2 of node N2) drops to the threshold TH2, it means that an overvoltage event occurs in the circuit, so the overvoltage protection signal OVP is immediately issued to activate the protection mechanism.

[0123] It should be noted that Figure 7B The node voltage VN2 of the node N2 rises during the period from t1 to t3, which means that the voltage across the battery B1 (VN2-VN1) adjacent to the node N2 will decrease. At this time, the protection circuit 112 may be triggered to issue the open line protection signal OWP, depending on which of the two is triggered first to cause the logic circuit 14 to issue the protection signal PT.

[0124] As for the situation where other pins in the battery secondary protection circuit 1 and the battery welding points fall off, the same can be applied and will not be described in detail here.

[0125] Another specific embodiment of the present invention is an operation method of a secondary battery protection circuit. In this embodiment, the secondary battery protection circuit includes a first pin and a second pin, which are respectively coupled to two ends of a first battery. A first current source is coupled between the first pin and the second pin.

[0126] Please refer to Figure 8 , Figure 8 This is a flow chart of the operation method of the battery secondary protection circuit in this embodiment. Figure 8 As shown, the operation method includes the following steps:

[0127] Step S10: providing a first sensing signal and a second sensing signal respectively;

[0128] Step S12: generating a first enabling signal according to the first sensing signal; and

[0129] Step S14 : When the first current is provided in response to the first enabling signal, a first protection signal is generated according to a second sensing signal changed by the first current.

[0130] In one embodiment, when the first current is provided, the operation method provides an open line protection signal according to the comparison result of the second sensing signal and the first threshold value, but the method is not limited thereto. In addition, in step S10, the operation method also provides a third sensing signal; in step S14, the operation method also provides an overvoltage protection signal according to the comparison result of the third sensing signal and the second threshold value; and sends a first protection signal according to the open line protection signal and / or the overvoltage protection signal, but the method is not limited thereto.

[0131] In one embodiment, the battery secondary protection circuit further includes a plurality of resistors connected in series and connected in parallel with the first current source. The operation method divides the first voltage and the second voltage by the plurality of resistors to provide a first sensing signal and a second sensing signal. In practical applications, the first sensing signal and the second sensing signal may have the same voltage value, but are not limited thereto.

[0132] In practical applications, the operation method of the secondary battery protection circuit generates the first enabling signal according to the comparison result between the first sensing signal and the third threshold. For example, when the first sensing signal is greater than the third threshold, the operation method of the secondary battery protection circuit generates the first enabling signal, but is not limited thereto.

[0133] Compared to the prior art, the battery secondary protection circuit of the present invention provides an open line protection function, which can continue to provide open line protection when the primary protection circuit fails. The battery secondary protection circuit operation method of the present invention will only activate the battery protection function (such as open line protection and / or overvoltage protection) when the cross-voltage of at least one battery reaches a preset threshold, thereby greatly reducing unnecessary power consumption. Compared with the method of simply combining the open line protection circuit and the overvoltage protection circuit, the present invention can reduce power consumption by about 50% to 60%, can achieve energy saving and power saving effects while providing overvoltage and open line protection functions at the same time, and is particularly suitable for portable devices powered by lithium batteries (such as electric drills and other tools that generate vibrations).

Claims

1. A battery secondary protection circuit, characterized in that: The above-mentioned battery secondary protection circuit comprises: A first pin and a second pin are respectively coupled to two ends of a first battery; a first sensing circuit coupled between the first pin and the second pin, and providing a first sensing signal, a second sensing signal and a third sensing signal respectively; A first current source, coupled between the first pin and the second pin and providing a first current; a first enabling circuit, coupled to the first sensing circuit and the first current source respectively, and generating a first enabling signal according to the first sensing signal; and A first protection circuit is coupled to the first sensing circuit, wherein when the first enabling signal enables the first current source, the first protection circuit generates a first protection signal based on the second sensing signal and the third sensing signal caused by the change of the first current, wherein the first protection signal is an open line protection signal or an overvoltage protection signal.

2. The battery secondary protection circuit according to claim 1, characterized in that: The first protection circuit includes a first comparator. When the first current source is enabled, the first comparator provides an open-line protection signal according to a comparison result between the second sensing signal and a first threshold.

3. The battery secondary protection circuit according to claim 1, characterized in that: The first protection circuit includes a second comparator. The second comparator provides an overvoltage protection signal according to a comparison result between the third sensing signal provided by the first sensing circuit and a second threshold.

4. The battery secondary protection circuit according to claim 1, characterized in that: The above-mentioned battery secondary protection circuit also includes: a third pin, wherein the second pin and the third pin are respectively coupled to two ends of a second battery; a second sensing circuit coupled between the second pin and the third pin, and providing a fourth sensing signal and a fifth sensing signal according to a second voltage on the second pin and a third voltage on the third pin; a second enabling circuit coupled to the second sensing circuit, generating a second enabling signal when the fourth sensing signal is greater than a fourth threshold; and A second protection circuit is coupled to the second sensing circuit and generates a second protection signal according to the fifth sensing signal when the first current source is enabled.

5. The battery secondary protection circuit according to claim 4, characterized in that: The above-mentioned battery secondary protection circuit also includes: A logic circuit is coupled to the first enabling circuit and the second enabling circuit respectively, and sends an enabling signal when receiving at least one of the first enabling signal and the second enabling signal to enable the first current source.

6. The battery secondary protection circuit according to claim 4, characterized in that: The battery secondary protection circuit also includes a second current source coupled between the second pin and the third pin, wherein a second current provided by the second current source is not equal to the first current, wherein either the first enable signal or the second enable signal simultaneously enables the first current source and the second current source.

7. The battery secondary protection circuit according to claim 1, characterized in that: The first sensing circuit includes a plurality of resistors connected in series and connected in parallel with the first current source, and performs voltage division according to a first voltage on the first pin and a second voltage on the second pin to provide the first sensing signal and the second sensing signal.

8. The battery secondary protection circuit according to claim 1, characterized in that: The first sensing signal and the second sensing signal have the same voltage value.

9. The battery secondary protection circuit according to claim 1, characterized in that: The first sensing signal and the second sensing signal changed by the first current have different voltage values.

10. The battery secondary protection circuit according to claim 1, characterized in that: The first current is a pulse signal with an adjustable duty cycle.

11. A method for operating a secondary battery protection circuit, characterized in that: The battery secondary protection circuit comprises a first pin and a second pin, which are respectively coupled to two ends of a first battery. A first current source is coupled between the first pin and the second pin and provides a first current. The operation method comprises the following steps: (a) providing a first sensing signal, a second sensing signal and a third sensing signal respectively; (b) generating a first enabling signal according to the first sensing signal; as well as (c) When the first current is provided in response to the first enabling signal, an open line protection signal is provided according to a comparison result between the second sensing signal changed by the first current and a first threshold, and an overvoltage protection signal is provided according to a comparison result between the third sensing signal and a second threshold, and a first protection signal is generated through a logic OR operation.

12. The operating method according to claim 11, characterized in that: The above operation method further includes the following steps: When the first current is provided, an open line protection signal is provided according to a comparison result between the second sensing signal and a first threshold.

13. The operating method according to claim 12, characterized in that: The above operation method further includes the following steps: In the above step (a), a third sensing signal is also provided; and In the step (c), an over-voltage protection signal is provided according to a comparison result between the third sensing signal and a second threshold.

14. The operation method according to claim 11, characterized in that: The above operation method further includes the following steps: When the first sensing signal is greater than a third threshold, the first enabling signal is generated.

Images