Overcurrent protection circuit suitable for lithium battery

Abstract

The overcurrent protection circuit is characterized in that a current sampling unit is electrically connected with a second resistor, the second resistor is electrically connected with a comparator, a fifth resistor is electrically connected with a power supply voltage, the fifth resistor is electrically connected with a sixth resistor and a third resistor, the third resistor is electrically connected with the comparator, and the third resistor is electrically connected with the comparator. The comparator, the fourth resistor and the first capacitor are grounded at the same time, the comparator is connected with a power supply voltage, the comparator and the fourth resistor are electrically connected with the first diode, the first diode is electrically connected with the first capacitor, the first resistor and the trigger, the first resistor and the trigger are connected with the power supply voltage, and the trigger is grounded. The trigger is connected with a power supply voltage, the trigger is electrically connected with the main control unit, and the main control unit is electrically connected with the trigger, so that the over-current protection circuit has the advantages that the applicability is improved, and the processing of an over-current working condition is facilitated.

Description

Technical Field

[0001] The utility model belongs to the technical field of battery protection circuits, and in particular relates to an overcurrent protection circuit suitable for lithium batteries. Background Art

[0002] At present, with the development of lithium battery industry technology, lithium battery management system technology is developing faster and faster. There are two ways to protect lithium batteries from overcurrent: the first is to form a comparator circuit through an op amp, and the output of the comparator is processed by a single-chip microcomputer;

[0003] The second method is to use the current protection function built into the lithium battery analog front end such as the dedicated chip ML5238, BQ76930, etc.

[0004] However, the first method can process overcurrent signals, but for lithium battery applications, overcurrent generally requires a delay before protection and discharge cutoff. In this processing method, after overcurrent occurs, the comparator directly generates a signal to the microcontroller without delay. And after the overcurrent signal disappears, the signal of the op amp also disappears, which is not conducive to the processing of overcurrent conditions. In the second method, the dedicated chips ML5238 and BQ76930 can achieve overcurrent protection through the internal current protection function, but the other functions of these chips do not meet the requirements and are not suitable for some mid-to-high-end applications. Utility Model Content

[0005] The utility model provides an overcurrent protection circuit suitable for a lithium battery, which realizes the delayed judgment of the overcurrent of the lithium battery and the maintenance of the overcurrent signal.

[0006] The technical solution of the utility model is implemented as follows: an overcurrent protection circuit suitable for a lithium battery, comprising a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a comparator, a current sampling unit, a main control unit, a first diode, a trigger and a first capacitor, the current sampling unit is electrically connected to the second resistor, the second resistor is electrically connected to the comparator, the fifth resistor is electrically connected to the power supply voltage, the fifth resistor is electrically connected to the sixth resistor and the third resistor, the sixth resistor is grounded, the third resistor is electrically connected to the comparator, the comparator and the fourth resistor and the first capacitor are grounded at the same time, the comparator is connected to the power supply voltage, the comparator is electrically connected to the fourth resistor and the first diode, the first diode is electrically connected to the first capacitor, the first resistor and the trigger, the first resistor is connected to the trigger, the trigger is grounded, the trigger is connected to the power supply voltage, the trigger is electrically connected to the main control unit, and the main control unit is electrically connected to the trigger. When the current in the battery circuit exceeds a set threshold, the comparator will detect this situation and trigger a protection mechanism.

[0007] As a preferred embodiment, the comparator positive input terminal is electrically connected to the second resistor, the comparator reverse input terminal is electrically connected to the third resistor, the comparator positive power supply terminal is connected to the supply voltage, the comparator reverse power supply terminal is grounded together with the fourth resistor and the first capacitor, and the comparator output terminal is electrically connected to the fourth resistor and the first diode.

[0008] As a preferred embodiment, pin 14 of the trigger is connected to the power supply voltage, pin 6 of the trigger is grounded, pin 5 of the trigger and the first resistor are connected to the power supply voltage, pin 3 of the trigger is electrically connected to the first diode, the first capacitor and the first resistor, pin 4 of the trigger is electrically connected to the main control unit, pin 1 of the trigger is electrically connected to the main control unit, and pin 7 of the trigger is grounded.

[0009] As a preferred implementation, the cathode of the first diode is electrically connected to the comparator output terminal and the fourth resistor, and the anode of the first diode is electrically connected to pin 3 of the trigger, the first capacitor and the first resistor.

[0010] After adopting the above technical solution, the beneficial effect of the utility model is: solving the defects of the existing solution that there is no over-current delay, the over-current signal will not be maintained, and other functions of the dedicated chip do not meet the requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0012] Figure 1 The invention is an overcurrent protection circuit diagram suitable for lithium batteries.

[0013] Figure 1 In the figure, R1 is the first resistor; R2 is the second resistor; R3 is the third resistor; R4 is the fourth resistor; R5 is the fifth resistor; R6 is the sixth resistor; U2A is the comparator; U1A is the trigger; CY is the current sampling unit; ZK is the main control unit; C1 is the first capacitor. DETAILED DESCRIPTION

[0014] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0015] according to Figure 1 As shown, an overcurrent protection circuit suitable for a lithium battery includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a comparator U2A, a current sampling unit CY, a main control unit ZK, a first diode, a trigger U1A and a first capacitor C1, the current sampling unit CY is electrically connected to the second resistor R2, the second resistor R2 is electrically connected to the comparator U2A, the fifth resistor R5 is electrically connected to a power supply voltage, the fifth resistor R5 is electrically connected to the sixth resistor R6 and the third resistor R3, the sixth resistor R6 is grounded, and the third resistor R3 is electrically connected to the comparator U2A. The comparator U2A, the fourth resistor R4 and the first capacitor C1 are grounded at the same time, the comparator U2A is connected to the power supply voltage, the comparator U2A is electrically connected to the fourth resistor R4 and the first diode, the first diode is electrically connected to the first capacitor C1, the first resistor R1 and the trigger U1A, the first resistor R1 and the trigger U1A are connected to the power supply voltage, the trigger U1A is grounded, the trigger U1A is connected to the power supply voltage, the trigger U1A is electrically connected to the main control unit ZK, and the main control unit ZK is electrically connected to the trigger U1A. When the current in the battery circuit exceeds the set threshold, the comparator U2A will detect this and trigger the protection mechanism. The trigger U1A will notify the main control unit ZK, and the main control unit ZK will control the output to protect the battery, such as cutting off the circuit or limiting the current. This can effectively protect the lithium battery from damage caused by excessive current, extend the battery life and ensure safety.

[0016] The positive input terminal of the comparator U2A is electrically connected to the second resistor R2, the reverse input terminal of the comparator U2A is electrically connected to the third resistor R3, the positive power supply terminal of the comparator U2A is connected to the supply voltage, the reverse power supply terminal of the comparator U2A is grounded together with the fourth resistor R4 and the first capacitor C1, and the output terminal of the comparator U2A is electrically connected to the fourth resistor R4 and the first diode.

[0017] The trigger U1A14 pin is connected to the power supply voltage, the trigger U1A6 pin is grounded, the trigger U1A5 pin and the first resistor R1 are connected to the power supply voltage, the trigger U1A3 pin is electrically connected to the first diode, the first capacitor C1 and the first resistor R1, the trigger U1A4 pin is electrically connected to the main control unit ZK, the trigger U1A1 pin is electrically connected to the main control unit ZK, and the trigger U1A7 pin is grounded.

[0018] The cathode of the first diode is electrically connected to the output end of the comparator U2A and the fourth resistor R4, and the anode of the first diode is electrically connected to the trigger U1A3 pin, the first capacitor C1 and the first resistor R1. When the current in the circuit exceeds the set threshold, the comparator U2A will trigger the protection mechanism to control the state of the fourth resistor R4 and the first diode. At the same time, the trigger U1A receives the signal and communicates with the main control unit ZK to realize the protection and control functions of the circuit.

[0019] I_CUR is the current signal processed by the current sampling unit CY. This signal is a voltage signal. The larger the current, the higher the voltage signal. This signal enters the non-inverting input terminal of the operational amplifier through the second resistor R2. The fifth resistor R5 and the sixth resistor R6 provide a reference voltage through voltage division, which enters the inverting input terminal of the operational amplifier through the third resistor R3. The reference voltage can be set according to the voltage converted by the current sampling unit CY when overcurrent occurs. When the lithium battery is used normally, the current does not reach the overcurrent value, the I_CUR voltage is less than the reference voltage, and the output terminal of the comparator U2A outputs a low level. When the lithium battery is used, the load is too large or other reasons cause overcurrent, the I_CUR voltage is greater than the reference voltage, and the output terminal of the comparator U2A outputs a high level.

[0020] The usage of trigger U1A is shown in the figure. The set terminal of pin 6 is connected to GND, the data terminal of pin 5 is connected to the power supply voltage, the overcurrent output signal is connected to the negative end of the diode, and the positive end of the diode, pin 3, is used as the clock signal. Pin 4 is the reset signal, which is controlled by the main control part. Pin 1 is the output signal, which enters the main control part and is processed by the main control part.

[0021] When the output of comparator U2A is low, the anode of the diode is about 0.7V, and the voltage of the first capacitor C1 is also about 0.7V. Pin 1 of trigger U1A is low. When the output of comparator U2A outputs high, the first capacitor C1 starts to charge, and the voltage of the anode of the diode starts to rise from 0.7V. When the rising voltage is greater than 3.5V, pin 3 of trigger U1A recognizes a rising edge clock, and pin 1 of trigger U1A outputs a high level. This signal enters the microcontroller as an overcurrent signal, and the microcontroller performs corresponding overcurrent processing. The application characteristics of the trigger U1A are that when the rising edge of the clock at pin 3 triggers the output high, even if the high level of pin 3 disappears, pin 1 continues to maintain a high level output. Only when the reset pin 4 is set high, pin 1 outputs a low level.

[0022] The working process of the whole circuit is: when overcurrent occurs, the first capacitor C1 starts to be charged. When the overcurrent condition is interrupted, the first capacitor C1 is no longer charged, but discharged through the fourth resistor R4 to prepare for the next overcurrent judgment. When the overcurrent time is relatively long, the charging voltage of the first capacitor C1 is greater than 3.5V, the trigger U1A acts, and outputs a high level. Through this process, a delayed judgment of overcurrent can be realized, and the delay time can be changed by adjusting the size of the first capacitor C1. When the trigger U1A acts, I_SC remains at a high level, enters the main control part, and performs corresponding processing. When the main control part completes the processing, I_RST is controlled to output a high level, the trigger U1A is reset, and I_SC remains at a low level to prepare for the next judgment.

[0023] In the description of the present utility model, it should be understood that the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present utility model. In the description of the present utility model, unless otherwise specified and limited, it should be noted that the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a mechanical connection or an electrical connection, or it can be the internal communication of two elements, it can be a direct connection, or it can be an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0024] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An overcurrent protection circuit suitable for lithium batteries, characterized in that: It includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a comparator, a current sampling unit, a main control unit, a first diode, a trigger and a first capacitor, the current sampling unit is electrically connected to the second resistor, the second resistor is electrically connected to the comparator, the fifth resistor is electrically connected to the power supply voltage, the fifth resistor is electrically connected to the sixth resistor and the third resistor, the sixth resistor is grounded, the third resistor is electrically connected to the comparator, the comparator, the fourth resistor and the first capacitor are grounded at the same time, the comparator is connected to the power supply voltage, the comparator is electrically connected to the fourth resistor and the first diode, the first diode is electrically connected to the first capacitor, the first resistor and the trigger, the first resistor and the trigger are connected to the power supply voltage, the trigger is grounded, the trigger is connected to the power supply voltage, the trigger is electrically connected to the main control unit, and the main control unit is electrically connected to the trigger.

2. An overcurrent protection circuit suitable for lithium batteries according to claim 1, characterized in that: The comparator positive input terminal is electrically connected to the second resistor, the comparator reverse input terminal is electrically connected to the third resistor, the comparator positive power supply terminal is connected to the supply voltage, the comparator reverse power supply terminal is grounded together with the fourth resistor and the first capacitor, and the comparator output terminal is electrically connected to the fourth resistor and the first diode.

3. An overcurrent protection circuit suitable for lithium batteries according to claim 1, characterized in that: Pin 14 of the trigger is connected to the power supply voltage, pin 6 of the trigger is grounded, pin 5 of the trigger and the first resistor are connected to the power supply voltage, pin 3 of the trigger is electrically connected to the first diode, the first capacitor and the first resistor, pin 4 of the trigger is electrically connected to the main control unit, pin 1 of the trigger is electrically connected to the main control unit, and pin 7 of the trigger is grounded.

4. An overcurrent protection circuit suitable for lithium batteries according to any one of claims 1 to 3, characterized in that: The cathode of the first diode is electrically connected to the comparator output terminal and the fourth resistor, and the anode of the first diode is electrically connected to the trigger pin 3, the first capacitor and the first resistor.

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