A pre-charging system and a control method thereof

Abstract

The application discloses a pre-charging system and a control method thereof, which comprises a single-chip microcomputer, which is used for collecting the voltage of a pre-charging circuit and performing calculation, filtering and duty cycle adjustment of a PWM pulse control signal; the pre-charging circuit comprises a triode Q1, the base of the triode Q1 is connected with the single-chip microcomputer and receives the PWM pulse control signal; one end of a capacitor C1 connected with the collector of the triode Q1, the other end of the capacitor C1 is connected with an NMOS tube Q2 control loop, the PWM pulse control signal is coupled to the NMOS tube Q2 control loop through the capacitor C1, and the on-off of the NMOS tube Q2 in the NMOS tube Q2 control loop is controlled; the drain of the NMOS tube Q2 is connected with the positive pole of a battery group through a pre-charging resistor R10, and the source level is connected with a pre-charging capacitor group, and the time for charging the pre-charging capacitor group is controlled through the on-off of the NMOS tube Q2.

Description

Technical Field

[0001] This invention relates to the field of circuit technology, and more specifically to a pre-charge system and its control method. Background Technology

[0002] In a battery management system, a capacitor is usually connected to the load side of the battery. However, the capacitor may short-circuit or be damaged due to the surge of large current when the battery is powered on.

[0003] To avoid this problem, the main approach is to add a pre-charging circuit to pre-charge the capacitor before closing the relay in the main circuit. This method can limit the excessive inrush current at the moment of power-on. However, the selection of the pre-charging resistor is very demanding; an unsuitable selection can cause the pre-charging resistor to burn out. The pre-charging resistor needs to be large, which will occupy a lot of space. At the same time, the pre-charging resistor needs to be adjusted according to different loads and their connected capacitors, which is a cumbersome process and not very versatile. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a pre-charge system, comprising: a microcontroller for acquiring the voltage of the pre-charge circuit and performing calculations, filtering, and adjusting the duty cycle of a PWM pulse control signal; the pre-charge circuit includes a transistor Q1, the base of which is connected to the microcontroller to receive the PWM pulse control signal; the collector of the transistor Q1 is connected to one end of a capacitor C1, and the other end of the capacitor C1 is connected to the control circuit of an NMOS transistor Q2; the PWM pulse control signal is coupled to the control circuit of the NMOS transistor Q2 through the capacitor C1 to control the on / off state of the NMOS transistor Q2 in the control circuit; the drain of the NMOS transistor Q2 is connected to the positive terminal of the battery pack through a pre-charge resistor R10, and the source is connected to the pre-charge capacitor bank; the charging time of the pre-charge capacitor bank is controlled by the on / off state of the NMOS transistor Q2.

[0005] Preferably, the control circuit of the NMOS transistor Q2 further includes diode D2, diode D3, resistor R4, resistor R5, and capacitor C2. The anode of diode D2 is connected to the other end of capacitor C1, and the cathode is connected to one end of resistor R4, one end of resistor R5, and one end of capacitor C2. The other end of resistor R4 is connected to the gate of NMOS transistor Q2, and the other end of resistor R5 is connected to the source of NMOS transistor Q2, the other end of capacitor C2, and the anode of diode D3. The cathode of diode D3 is connected to the other end of capacitor C1.

[0006] Preferably, the source of the NMOS transistor Q2 is also connected to one end of a resistor R8, the other end of the resistor R8 is connected to one end of a resistor R9 and the voltage acquisition terminal of the microcontroller, and the other end of the resistor R9 is grounded.

[0007] Preferably, the pre-charge resistor R10 is connected to the battery pack via diode D4.

[0008] Preferably, the positive terminal of the diode D4 is connected to the battery pack, and the negative terminal is connected to the pre-charge resistor R10.

[0009] Preferably, the positive terminal of the diode D4 is also connected to one end of the resistor R6, the other end of the resistor R6 is connected to the voltage acquisition terminal of the microcontroller and one end of the resistor R7, and the other end of the resistor R7 is grounded.

[0010] Preferably, the collector of the transistor Q1 is also connected to one end of a resistor R3, the other end of the resistor R3 is connected to the negative terminal of the diode D1, and the positive terminal of the diode D1 is connected to a high level.

[0011] Preferably, the base of transistor Q1 is connected to one end of resistor R1, the other end of resistor R1 is connected to the output terminal of the single chip, the emitter of transistor Q1 is connected to one end of resistor R2, and the other end of resistor R2 is grounded.

[0012] Preferably, the pre-charge resistor R10 is a PTC resistor or a gold resistor.

[0013] A precharge control method is also provided, the control method being applicable to any of the precharge systems described in the above technical solutions, the method comprising:

[0014] S1. The microcontroller samples the voltage Vbat at the input terminal BAT+ of the battery pack and the voltage Vcap at the pre-charged capacitor pack CAP+ through the voltage acquisition terminal.

[0015] S2. The microcontroller calculates the voltage difference Vde lta between voltage Vbat and voltage Vcap.

[0016] S3. Determine the filter coefficient based on the resistance value of the pre-charge resistor R10, and the microcontroller performs low-pass filtering on the voltage difference Vde lta.

[0017] S4. Set the switching frequency of the PWM pulse module in the microcontroller, and the microcontroller outputs a PWM pulse control signal to the precharge circuit.

[0018] The technical effects and advantages of this invention are as follows:

[0019] This invention simplifies the precharge control loop through underlying drive circuit design combined with software sampling and pulse control, reducing system costs and the requirements for precharge resistors. It also reduces the number of control switches and precharge resistors. By using a microcontroller to acquire the voltage Vbat at the battery pack input terminal BAT+ and the voltage Vcap at the precharge capacitor bank CAP+, no additional hardware control loop is needed, significantly reducing product size. Only the maximum duty cycle needs to be determined based on the precharge resistor selection, making the precharge process controllable. The relationship between the precharge resistor selection and the maximum duty cycle can be parameterized, resulting in good applicability and reducing the need to select different precharge resistor values ​​each time due to varying capacitor values. This avoids the problems of system startup failure or precharge circuit burnout caused by different resistor values ​​in traditional precharge methods. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the pre-charging system provided in the embodiments of this application;

[0021] Figure 2 This is a circuit diagram of the pre-charging circuit in the pre-charging system provided in the embodiments of this application;

[0022] Figure 3 This is a schematic diagram of the control method of the pre-charge system provided in the embodiments of this application.

[0023] In the picture:

[0024] 1. Microcontroller; 2. Pre-charging circuit; 3. Battery pack; 4. Pre-charging capacitor pack. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and design various embodiments with various modifications suitable for a particular purpose.

[0026] Please see Figures 1-2This embodiment provides a pre-charging system, including a microcontroller 1 and a pre-charging circuit 2. The pre-charging circuit 2 is connected to a battery pack 3 and a pre-charging capacitor bank 4. The battery pack 3 provides power to the load through the pre-charging system and the pre-charging capacitor bank 4. The pre-charging circuit 2 includes a pre-charging resistor R10, which is connected to the battery pack 3 through a diode D4. In this embodiment, the pre-charging resistor R10 is a PTC resistor or a gold resistor, which has high temperature resistance. The microcontroller 1 is connected to the pre-charging circuit 2, collects and calculates the voltage difference of the pre-charging resistor R10, and performs calculations, filtering, and adjustment of the duty cycle of the PWM pulse control signal. Based on the voltage difference, it outputs a PWM pulse control signal to the pre-charging circuit 2. The pre-charge circuit 2 includes a transistor Q1, whose base is connected to the microcontroller 1 to receive PWM pulse control signals. The collector is connected to one end of a capacitor C1, and the other end of the capacitor C1 is connected to the NMOS transistor Q2 control circuit 201. The PWM pulse control signal is coupled to the NMOS transistor Q2 control circuit 201 through the capacitor C1 to control the on / off state of the NMOS transistor Q2 in the NMOS transistor Q2 control circuit 201. The drain of the NMOS transistor Q2 is connected to the positive terminal of the battery pack 3 through the pre-charge resistor R10, and the source is connected to the pre-charge capacitor pack 4. The charging time of the pre-charge capacitor pack 4 is controlled by the on / off state of the NMOS transistor Q2. The pre-charge capacitor pack 4 includes multiple capacitors connected in parallel.

[0027] The control circuit for NMOS transistor Q2 also includes diodes D2 and D3, resistors R4 and R5, and capacitor C2. The anode of diode D2 is connected to the other end of capacitor C1, and the cathode is connected to one end of resistor R4, one end of resistor R5, and one end of capacitor C2. The other end of resistor R4 is connected to the gate of NMOS transistor Q2, and the other end of resistor R5 is connected to the source of NMOS transistor Q2, the other end of capacitor C2, and the anode of diode D3. The cathode of diode D3 is connected to the other end of capacitor C1. The PWM pulse control signal is coupled through capacitor C1 to the voltage between diodes D2 and D3 to control NMOS transistor Q2 and reduce the interference of NMOS transistor Q2's turn-on and turn-off on the control circuit.

[0028] The source of NMOS transistor Q2 is also connected to one end of resistor R8. The other end of resistor R8 is connected to one end of resistor R9 and the voltage acquisition terminal of microcontroller 1. The other end of resistor R9 is grounded.

[0029] The positive terminal of diode D4 is connected to battery pack 3 and one end of resistor R6, and the negative terminal is connected to pre-charge resistor R10. The other end of resistor R6 is connected to the voltage acquisition terminal of microcontroller 1 and one end of resistor R7. The other end of resistor R7 is grounded.

[0030] The collector of transistor Q1 is connected to one end of resistor R3, the base is connected to one end of resistor R1, the emitter is connected to one end of resistor R2, the other end of resistor R3 is connected to the negative terminal of diode D1, the positive terminal of diode D1 is connected to a high level, the other end of resistor R1 is connected to the output terminal of the single chip, and the other end of resistor R2 is grounded.

[0031] Please see Figure 3 This embodiment provides a control method for a pre-charge system, the method comprising:

[0032] S1. The microcontroller 1 samples the voltage Vbat at the input terminal BAT+ of battery pack 3 and the voltage Vcap at the pre-charged capacitor pack 4CAP+ through the voltage acquisition terminal.

[0033] S2. The microcontroller calculates the voltage difference Vde lta between voltages Vbat and Vcap.

[0034] S3. Determine the filter coefficient based on the resistance value of the pre-charge resistor R10, and perform low-pass filtering on the voltage difference Vde lta by the microcontroller 1.

[0035] S4. Set the switching frequency of the PWM pulse module in microcontroller 1, and output the PWM pulse control signal to the precharge circuit 2.

[0036] In step S2, the voltage difference Vde lta is calculated using the formula Vde lta = Vbat - Vcap. In step S3, the filter coefficient can be selected as 1Hz. In step S4, the switching frequency of the PWM pulse module can be set to 500Hz. The microcontroller 1 adjusts the duty cycle of the PWM pulse according to the filtered voltage. The larger the voltage difference Vde lta, the smaller the duty cycle. Therefore, the maximum duty cycle depends on the selection of the pre-charge resistor R10. The pre-charge system and control method provided by this invention can be flexibly adjusted according to different models of the pre-charge resistor R10 to ensure that the pre-charge resistor R10 is within its rated operating condition.

[0037] This invention controls the switching on and off of NMOS transistor Q2 via capacitive coupling, reducing interference from Q2's switching on and off to the control loop. It uses a microcontroller 1 to acquire the voltage Vbat at the battery pack input terminal BAT+ and the voltage Vcap at the pre-charge capacitor bank CAP+, eliminating the need for additional hardware control loops. The algorithm is simple, requiring only the selection of the pre-charge resistor R10 to determine the maximum duty cycle. The pre-charge process is controllable, and the relationship between the selection of the pre-charge resistor R10 and the maximum duty cycle can be parameterized, resulting in good applicability.

[0038] Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art and related fields based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described and explained in the present invention, unless otherwise specified or limited, shall be implemented according to conventional means in the art.

Claims

1. A pre-charge system, characterized in that, include: The microcontroller (1) is used to collect the voltage of the pre-charging circuit (2) and perform calculations, filtering and adjustment of the duty cycle of the PWM pulse control signal; The pre-charging circuit (2) includes a transistor Q1, the base of which is connected to the microcontroller (1) to receive the PWM pulse control signal; The collector of transistor Q1 is connected to one end of capacitor C1, and the other end of capacitor C1 is connected to the control circuit (201) of NMOS transistor Q2. The PWM pulse control signal is coupled to the control circuit (201) of NMOS transistor Q2 through capacitor C1 to control the on and off of NMOS transistor Q2 in the control circuit (201). The drain of the NMOS transistor Q2 is connected to the positive terminal of the battery pack (3) through the pre-charge resistor R10, and the source is connected to the pre-charge capacitor pack (4). The charging time of the pre-charge capacitor pack (4) is controlled by the on / off state of the NMOS transistor Q2.

2. The pre-charge system according to claim 1, characterized in that, The NMOS transistor Q2 control circuit (201) further includes diode D2, diode D3, resistor R4, resistor R5, and capacitor C2. The anode of diode D2 is connected to the other end of capacitor C1, and the cathode is connected to one end of resistor R4, one end of resistor R5, and one end of capacitor C2. The other end of resistor R4 is connected to the gate of NMOS transistor Q2, and the other end of resistor R5 is connected to the source of NMOS transistor Q2, the other end of capacitor C2, and the anode of diode D3. The cathode of diode D3 is connected to the other end of capacitor C1.

3. The pre-charge system according to claim 1, characterized in that, The source of the NMOS transistor Q2 is also connected to one end of a resistor R8. The other end of the resistor R8 is connected to one end of a resistor R9 and the voltage acquisition terminal of the microcontroller (1). The other end of the resistor R9 is grounded.

4. A pre-charge system according to claim 3, characterized in that, The pre-charge resistor R10 is connected to the battery pack (3) via diode D4.

5. A pre-charge system according to claim 4, characterized in that, The positive terminal of the diode D4 is connected to the battery pack (3), and the negative terminal is connected to the pre-charge resistor R10.

6. A pre-charge system according to claim 5, characterized in that, The positive terminal of the diode D4 is also connected to one end of the resistor R6. The other end of the resistor R6 is connected to the voltage acquisition terminal of the microcontroller (1) and one end of the resistor R7. The other end of the resistor R7 is grounded.

7. A pre-charge system according to claim 1, characterized in that, The collector of the transistor Q1 is also connected to one end of a resistor R3, and the other end of the resistor R3 is connected to the negative terminal of the diode D1, with the positive terminal of the diode D1 connected to a high level.

8. A pre-charge system according to claim 7, characterized in that, The base of transistor Q1 is connected to one end of resistor R1, the other end of resistor R1 is connected to the output terminal of the chip, the emitter of transistor Q1 is connected to one end of resistor R2, and the other end of resistor R2 is grounded.

9. A pre-charge system according to claim 1, characterized in that, The pre-charge resistor R10 is a PTC resistor or a gold resistor.

10. A pre-charge control method, characterized in that, The control method is applicable to any of the pre-charge systems described in claims 1-9 above, and the method includes: S1, The microcontroller (1) samples the voltage Vbat of the battery pack (3) input terminal BAT+ and the voltage Vcap of the pre-charged capacitor pack (4) CAP+ through the voltage acquisition terminal; S2, The single-chip microcomputer (1) calculates the voltage difference Vdelta between voltage Vbat and voltage Vcap; S3. Determine the filter coefficient based on the resistance value of the pre-charge resistor R10. The microcontroller (1) performs low-pass filtering on the voltage difference Vdelta. S4. Set the switching frequency of the PWM pulse module in the microcontroller (1), and the microcontroller (1) outputs a PWM pulse control signal to the pre-charge circuit (2).

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