Lithium battery ESD protection circuit

Abstract

The utility model discloses a lithium battery ESD protection circuit, the lithium battery comprises a positive electrode PACK + and a negative electrode PACK-, the positive electrode PACK + is connected in series with a charging MOS tube Q1 and a discharging MOS tube Q2, the MOS tube Q1 and the MOS tube Q2 which are connected in series are integrally connected in parallel with a capacitor C1, and the positive electrode PACK + and the negative electrode PACK-are connected through a capacitor C2. The wiring of the circuit where the capacitor C1 and the capacitor C2 are located is coated with copper, and the wiring is widened and shortened as much as possible under the limitation of the size of the circuit board and the component. According to the utility model, the capacitor C1 is connected in parallel at the two ends of the charging MOS tube Q1 and the discharging MOS tube Q2, and the wiring or the clad copper connected with the capacitor is as wide as possible and as short as possible, so that the MOS tubes can be protected due to the characteristic of alternating current short circuit of the capacitor. A capacitor C2 is connected between the positive electrode PACK + and the negative electrode PACK-, and when ESD is conducted at the PACK + end, the capacitors provide shunt branches. Wiring or clad copper for connecting the capacitors is as wide as possible and as short as possible. Therefore, the protection level of the ESD is well improved.

Description

Technical Field

[0001] The utility model relates to the field of lithium battery protection, and particularly relates to a lithium battery ESD protection circuit. Background Art

[0002] With the continuous development of electronic technology, the requirements for ESD protection of lithium battery packs in actual use are getting higher and higher. Most of the existing ESD electrostatic protections are solved by adding electrostatic protection diodes.

[0003] During the development of the lithium battery protection board, since the lithium battery needs to be applicable to different environmental scenarios, the requirements for the ESD protection level are different. For general electronic products passing the CTA certification, the electrostatic level is required to be 3, that is, 6KV for contact and 8KV for air. Since electrostatic discharge will generate an instantaneous large current, the energy may damage the circuit and directly destroy the normal use of the device. On the other hand, since there are also high-frequency pulses in the static electricity, the magnetic fields caused by these pulses cause electromagnetic interference to the surrounding fields through coupling, radiation, etc., and cause interference to the device through gaps, circuits, etc., resulting in temporary failure of the device. Therefore, it is necessary to design a circuit that can improve the ESD protection level without using electrostatic protection diodes. Summary of the Utility Model

[0004] The purpose of the utility model is to provide a lithium battery ESD protection circuit that can improve the ESD protection level without using electrostatic protection diodes.

[0005] The technical solution of the utility model is as follows:

[0006] A lithium battery ESD protection circuit, the lithium battery includes positive and negative electrodes PACK +, PACK-, wherein charging and discharging MOS transistors Q1, Q2 are connected in series on the positive electrode PACK +, and a capacitor C1 is connected in parallel to the series-connected MOS transistors Q1, Q2, and the positive and negative electrodes PACK +, PACK- are connected through a capacitor C2.

[0007] Preferably, the capacitor C1 is replaced by a plurality of capacitors connected in series.

[0008] Preferably, the capacitor C2 is replaced by a plurality of capacitors connected in series.

[0009] Preferably, the traces of the lines where the capacitors C1 and C2 are located are copper-clad, and under the limitation of the circuit board and component sizes, they are widened as much as possible and shortened as much as possible.

[0010] Preferably, the charging and discharging MOS transistors Q1, Q2 are connected and controlled by a battery management unit (BMU), and the battery management unit (BMU) collects the battery current and voltage.

[0011] The advantages of the utility model are:

[0012] For the present utility model, capacitors C1 are connected in parallel across the charging and discharging MOS transistors Q1 and Q2, and the traces or copper cladding connecting the capacitors are also made as wide and as short as possible. Due to the characteristic of AC short - circuit of the capacitors, protection is provided for the MOS transistors. A capacitor C2 is connected between the positive and negative terminals PACK+ and PACK-. When an ESD occurs at the PACK+ terminal, these capacitors provide a shunt path. The traces or copper cladding connecting these capacitors are also made as wide and as short as possible. In this way, the ESD protection level is well improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present utility model will be further described below in conjunction with the drawings and embodiments:

[0014] Figure 1 It shows the current flow direction of the ESD protection circuit of the lithium - battery of the present utility model when an ESD occurs at PACK+;

[0015] Figure 2 It shows the current flow direction of the ESD protection circuit of the lithium - battery of the present utility model when an ESD occurs at PACK-. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] When an ESD occurs, the ESD current usually flows to the place with the largest capacitance value, that is, to the battery cell. And the ESD current will choose the path with the lowest impedance. Therefore, wide traces or copper cladding, because of their low impedance and low inductance, can guide the ESD current to the battery cell, thus preventing the ESD current from flowing into other ESD - sensitive electronic components and causing device damage.

[0017] As Figure 1 and 2 shown, for the ESD protection circuit of the lithium - battery of the present utility model, the lithium - battery includes positive and negative terminals PACK+ and PACK-, where charging and discharging MOS transistors Q1 and Q2 are connected in series on the positive terminal PACK+. The charging and discharging MOS transistors Q1 and Q2 are connected and controlled by a battery management unit (BMU), and the battery management unit (BMU) collects the battery current and voltage. To implement the ESD protection circuit, the present utility model adopts the following solutions.

[0018] The series - connected MOS transistors Q1 and Q2 are integrally connected in parallel with a capacitor C1, and the positive and negative terminals PACK+ and PACK - are connected through a capacitor C2. The capacitors C1 and C2 usually adopt two capacitors connected in series to prevent the protection function from failing due to the short - circuit of one of the capacitors.

[0019] Figure 1 and Figure 2They are the current directions when ESD is applied to PACK+ and PACK- respectively. In both cases, the current paths are similar. Since a large current needs to flow, the traces or copper cladding of MOS transistors Q1 and Q2 are relatively wide. The capacitor C1 connected in parallel across MOS transistors Q1 and Q2 forms protection for MOS transistors Q1 and Q2 due to its AC short-circuit characteristic. However, the premise is that the traces or copper cladding connecting capacitor C1 are also as wide and as short as possible. The capacitors on PACK+ and PACK- are equally important. When ESD is applied to the PACK+ terminal, these capacitors provide shunt branches. The traces or copper cladding connecting these capacitors are also as wide and as short as possible. In this way, the ESD protection level is improved well.

[0020] The above embodiments are only used to illustrate the technical concept and characteristics of the present invention, and the purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. All modifications made according to the spirit of the main technical solution of the present invention should be covered within the protection scope of the present invention.

Claims

1. A lithium battery ESD protection circuit, the lithium battery comprises a positive and negative electrode PACK+, PACK-, wherein the positive electrode PACK+ is connected in series with a charge and discharge MOS tube Q1, Q2, characterized in that: The MOS tubes Q1 and Q2 connected in series are connected in parallel with a capacitor C1 as a whole, and the positive and negative electrodes PACK+ and PACK- are connected via a capacitor C2.

2. The lithium battery ESD protection circuit according to claim 1, characterized in that: The capacitor C1 is replaced by a plurality of capacitors connected in series.

3. The lithium battery ESD protection circuit according to claim 2, characterized in that: The capacitor C2 is replaced by a plurality of capacitors connected in series.

4. The lithium battery ESD protection circuit according to claim 3, characterized in that: The copper wiring of the circuits where the capacitors C1 and C2 are located is widened and shortened as much as possible within the size constraints of the circuit board and components.

5. The lithium battery ESD protection circuit according to claim 1, characterized in that: The charging and discharging MOS tubes Q1 and Q2 are connected and controlled by a battery management unit (BMU), and the battery management unit (BMU) collects battery current and voltage.

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