Undervoltage protection circuit for a drive power supply

Abstract

The application discloses an under-voltage protection circuit of a driving power supply. The under-voltage protection circuit comprises a voltage detection module, a main control module, a level conversion module and a power driving module. The input end of the voltage detection module is electrically connected with a driving power supply end. The input end of the main control module is electrically connected with the output end of the voltage detection module. The enable end of the level conversion module is electrically connected with the output end of the voltage detection module, and the input end of the level conversion module is electrically connected with the output end of the main control module. The first input end of the power driving module is electrically connected with the output end of the level conversion module, the second input end of the power driving module is electrically connected with the driving power supply end, and the output end of the power driving module is electrically connected with a power device. The voltage detection module outputs an under-voltage detection result when the driving power supply is less than a preset threshold. The main control module stops outputting a first control signal in response to the under-voltage detection result. The level conversion module stops the level conversion and output of the first control signal in response to the under-voltage detection result, so that the power driving module stops driving the power device. According to the application, the power device can be quickly and reliably protected.

Description

Technical Field

[0001] This application belongs to the field of power electronics technology, and in particular relates to an undervoltage protection circuit for a drive power supply. Background Technology

[0002] In the operation of a motor control system, the drive power supply is crucial, ensuring the switching on and off of critical power devices. Taking an Insulated Gate Bipolar Transistor (IGBT) as an example, the drive power supply applies a voltage (such as 15V) to the gate of the IGBT, thereby driving the IGBT to conduct.

[0003] However, when the drive power supply is undervoltage, the IGBT cannot obtain sufficient drive voltage, resulting in insufficient conduction, which will accelerate the aging of the device and even directly cause the device to fail, thereby affecting the stability and reliability of the entire motor control system.

[0004] The relevant technologies cannot provide fast and reliable protection for power devices when performing voltage detection and undervoltage protection on the drive power supply. Utility Model Content

[0005] This application provides an undervoltage protection circuit for a drive power supply, which can quickly stop emitting waves when undervoltage occurs through dual hardware and software protection, thus achieving fast and reliable protection for power devices.

[0006] In a first aspect, embodiments of this application provide an undervoltage protection circuit for a drive power supply, comprising: The voltage detection module has its input terminal electrically connected to the drive power supply terminal; The main control module has its input terminal electrically connected to the output terminal of the voltage detection module; The level conversion module has its enable terminal electrically connected to the output terminal of the voltage detection module, and its input terminal electrically connected to the output terminal of the main control module. The power drive module has its first input terminal electrically connected to the output terminal of the level conversion module, its second input terminal electrically connected to the drive power supply terminal, and its output terminal electrically connected to the power device. The voltage detection module is configured to output an undervoltage detection result when the driving power supply is less than a preset threshold. The main control module is configured to stop outputting the first control signal in response to the undervoltage detection result. The level conversion module is configured to stop level conversion and output of the first control signal in response to the undervoltage detection result, so that the power drive module stops driving the power device.

[0007] In one possible embodiment of the first aspect, the voltage detection module includes a voltage regulator module, an isolation device, and a first resistor: The first side of the voltage regulator module and the isolation device is connected in series between the drive power supply terminal and the first ground terminal; The first end of the first resistor is electrically connected to the reference power supply terminal, and the second end of the first resistor serves as the output terminal of the voltage detection module. The second side of the isolation device is connected in series between the second terminal of the first resistor and the second ground terminal.

[0008] In one possible embodiment of the first aspect, the voltage regulator module includes a second resistor and a Zener diode; The second resistor, the Zener diode, and the first side of the isolation device are connected in series between the drive power supply terminal and the first ground terminal.

[0009] In one possible embodiment of the first aspect, the voltage detection module further includes: The third resistor is connected in parallel with the first side of the isolation device.

[0010] In one possible embodiment of the first aspect, the voltage detection module further includes a fourth resistor and a capacitor: The fourth resistor has its first end electrically connected to the second end of the first resistor, and its second end serves as the output terminal of the voltage detection module. The capacitor is electrically connected between the second terminal of the fourth resistor and the second ground terminal.

[0011] In one possible embodiment of the first aspect, the isolation device includes an optocoupler.

[0012] In one possible embodiment of the first aspect, the power drive module includes a drive chip electrically connected to a first ground terminal.

[0013] In one possible embodiment of the first aspect, the main control module includes a main control chip, which is electrically connected to a second ground terminal.

[0014] In one possible embodiment of the first aspect, the level conversion module includes: The three-state buffer has its enable terminal electrically connected to the output terminal of the voltage detection module, its input terminal electrically connected to the output terminal of the main control module, and its output terminal electrically connected to the first input terminal of the power drive module.

[0015] In one possible embodiment of the first aspect, The voltage detection module is configured to output a normal detection result when the driving power supply is less than a preset threshold. The main control module outputs a first control signal in response to the normal detection result. The level conversion module converts the first control signal to obtain a second control signal and outputs it in response to the normal detection result. The power drive module converts the second control signal to obtain a third control signal according to the driving power supply and drives the power device according to the third control signal.

[0016] This application describes an undervoltage protection circuit for a drive power supply. The undervoltage protection circuit includes a voltage detection module, a main control module, a level conversion module, and a power drive module. The input terminal of the voltage detection module is electrically connected to the drive power supply terminal and is used to detect the drive power supply. It can output a corresponding detection result (referred to as an undervoltage detection result) when the drive power supply voltage is below a preset threshold. The output terminal of the voltage detection module is electrically connected to both the input terminal of the main control module and the enable terminal of the level conversion module, meaning the undervoltage detection result can be simultaneously notified to both the main control module and the enable terminal of the level conversion module. The software logic in the main control module prevents the transmission of a waveform upon receiving the undervoltage detection result; that is, it does not output the first control signal (such as PWM1) to the input terminal of the level conversion module, thus preventing the level conversion module from transmitting a waveform. This can be achieved by stopping the waveform transmission in software to protect the power devices. Simultaneously, the control terminal of the level conversion module does not operate upon receiving the undervoltage detection result, therefore it cannot perform level conversion and output the first control signal. This can be achieved by stopping the waveform transmission in hardware to protect the power devices. The first input terminal of the power drive module is electrically connected to the output terminal of the level conversion module, the second input terminal of the power drive module is electrically connected to the drive power supply terminal, and the output terminal of the power drive module is electrically connected to the power device. Therefore, when the level conversion module does not generate a wave, the power drive module does not drive the power device. Thus, through hardware and software double protection, the power device is quickly stopped from generating a wave when there is an undervoltage. Attached Figure Description

[0017] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings, in which the same or similar reference numerals denote the same or similar features, and the drawings are not drawn to scale.

[0018] Figure 1 This is a schematic diagram of an undervoltage protection circuit for a drive power supply provided in an embodiment of this application; Figure 2 This is another schematic diagram of the undervoltage protection circuit of the driving power supply provided in the embodiments of this application; Figure 3 This is another schematic diagram of the undervoltage protection circuit of the driving power supply provided in the embodiments of this application; Figure 4 This is another schematic diagram of the undervoltage protection circuit of the driving power supply provided in the embodiments of this application; Figure 5 This is another schematic diagram of the undervoltage protection circuit of the driving power supply provided in the embodiments of this application; Figure 6 This is another schematic diagram of the undervoltage protection circuit of the driving power supply provided in the embodiments of this application; Figure 7 This is another schematic diagram of the undervoltage protection circuit of the driving power supply provided in the embodiments of this application. Detailed Implementation

[0019] The features and exemplary embodiments of various aspects of this application will now be described in detail. To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain this application and are not configured to limit this application. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples of this application.

[0020] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0021] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0022] Various modifications and variations can be made to this application without departing from its spirit or scope, which will be apparent to those skilled in the art. Therefore, this application is intended to cover modifications and variations falling within the scope of the corresponding claims (the claimed technical solutions) and their equivalents. It should be noted that the implementation methods provided in the embodiments of this application can be combined with each other without contradiction.

[0023] Before describing the technical solutions provided in the embodiments of this application, in order to facilitate understanding of the embodiments of this application, this application first specifically explains the problems existing in the related technologies: In the operation of a motor control system, the drive power supply is crucial, ensuring the switching on and off of critical power devices. Taking an Insulated Gate Bipolar Transistor (IGBT) as an example, the drive power supply applies a voltage (such as 15V) to the gate of the IGBT, thereby driving the IGBT to conduct.

[0024] However, when the drive power supply is undervoltage, the IGBT cannot obtain sufficient drive voltage, resulting in insufficient conduction, which will accelerate the aging of the device and even directly cause the device to fail, thereby affecting the stability and reliability of the entire motor control system.

[0025] In some related technologies, the undervoltage fault strategy for the drive power supply employs a highly integrated drive chip, such as the Nanochip Micro-Capacitive series, equipped with a working status feedback pin (such as the Ready pin, or RDY pin for short). A low-level active signal indicates an undervoltage fault. When an undervoltage fault occurs, the working status feedback pin remains low, allowing the main control chip to detect the fault and stop transmitting signals. Furthermore, the RST / EN pins of the drive chip need to be pulled up again before the chip can be reused. While this drive chip can detect faults, its high cost is a drawback. For example, in scenarios where multiple chips are used in a single system, six drive chips are required for the three-phase output upper and lower bridges. Therefore, while highly integrated isolated drive chips have internal drive power detection capabilities, their cost is relatively high for systems using multiple chips. With the development of the new energy industry, the demand for motor controllers is increasing, making cost reduction an important research direction in the design of isolated drive power supplies.

[0026] In light of this, some related technologies employ software for voltage sampling and undervoltage protection of the power supply. A voltage regulation module adjusts the analog voltage signal before sending it to the main control chip to determine whether to terminate the waveform transmission. While this reduces costs, pure software-based judgment and command generation are slow and not entirely reliable. Other related technologies use hardware for voltage sampling and undervoltage protection. Hardware circuits determine the voltage threshold and then send the fault level to the main control chip to determine whether to terminate operation. Although hardware circuits are fast, they require isolated operational amplifiers and comparators, resulting in higher costs.

[0027] Therefore, the related technologies suffer from problems such as excessive cost and inability to provide fast and reliable protection for power devices when performing voltage sampling and undervoltage protection of the drive power supply.

[0028] Based on this, the embodiments of this application provide an undervoltage protection circuit for a drive power supply, which can quickly stop emitting waves when undervoltage occurs through dual hardware and software protection, thereby achieving fast and reliable protection for power devices.

[0029] The undervoltage protection circuit of the driving power supply provided in the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0030] Figure 1 This is a schematic diagram of an undervoltage protection circuit for a drive power supply provided in an embodiment of this application, as shown below. Figure 1 As shown, the undervoltage protection circuit 100 of the drive power supply may include a voltage detection module 10, a main control module 20, a level conversion module 30, and a power drive module 40.

[0031] The driving power supply can be used to drive the power device 200. For example, the power drive module 40 can apply a power supply (such as 15V) to the gate of the IGBT to drive it to conduct. When the power supply is undervoltage, the IGBT will not conduct sufficiently, which will damage the IGBT.

[0032] The input terminal of the voltage detection module 10 is electrically connected to the drive power supply terminal.

[0033] For example, the voltage detection module 10 is used to detect the voltage of the drive power supply at the drive power supply terminal and obtain the detection result. The detection result may include normal voltage (e.g., low level) or undervoltage (e.g., high level). The detection result can be simultaneously sent to the main control module 20 and the level conversion module 30.

[0034] The input terminal of the main control module 20 is electrically connected to the output terminal of the voltage detection module 10.

[0035] For example, the main control module 20 may include a main control chip 21, which is used to generate a wave. For instance, the main control chip 21 can generate a pulse width modulation wave (PWM) with a voltage amplitude of 3.3V, which can be denoted as the first control signal PWM1. When the main control module 21 receives a detection result from the voltage detection module 10 indicating that the voltage is normal, it will output PWM1; when it receives a detection result from the voltage detection module 10 indicating that the voltage is undervoltage, it will stop outputting PWM1.

[0036] The enable terminal of the level conversion module 30 is electrically connected to the output terminal of the voltage detection module 10, and the input terminal of the level conversion module 30 is electrically connected to the output terminal of the main control module 20.

[0037] For example, the level conversion module 30 can be used to convert the first control signal PWM1 output by the main control chip 21 to obtain a second control signal PWM2. PWM1 and PWM2 have the same duty cycle but different voltage amplitudes. For example, the voltage amplitude of PWM1 is 3.3V and the voltage amplitude of PWM2 is 5V. When the voltage detection module 10 detects that the voltage is normal, the level conversion module 30 will convert PWM1 to obtain PWM2 and output PWM2. When the voltage detection module 10 detects that the voltage is undervoltage, the level conversion module 30 will stop working (stop the level conversion and output of PWM1).

[0038] The first input terminal of the power drive module 40 is electrically connected to the output terminal of the level conversion module 30, the second input terminal of the power drive module 40 is electrically connected to the drive power supply terminal, and the output terminal of the power drive module 40 is electrically connected to the power device 200.

[0039] For example, the power drive module 40 may include a drive chip 41. The drive chip 41 can use a drive power supply (e.g., 15V) to perform level conversion on the second control signal PWM2 to obtain a third control signal PWM3 and output it to the control terminal (e.g., the gate of an IGBT) of the power module 200. PWM2 and PWM3 have the same duty cycle but different voltage amplitudes. For example, if the drive power supply is 15V, the voltage amplitude of PWM1 is 3.3V, the voltage amplitude of PWM2 is 5V, and the voltage amplitude of PWM3 is 15V. When the voltage detection module 10 detects that the voltage is normal, the main control chip 21 will output the first control signal PWM1. The level conversion module 30 will perform level conversion on PWM1 to obtain PWM2. The power drive module 40 will perform level conversion on the second control signal PWM2 to obtain the third control signal PWM3 and output it to the control terminal of the power module 200 to drive the power device. If the voltage detection module 10 detects that the voltage is undervoltage (the driving power supply is less than the preset threshold), the main control module 20 stops transmitting waves through software control (stops outputting the first control signal PWM1). At the same time, the level conversion module 30 can stop the level conversion and output of the first control signal PWM1 through hardware circuitry, so that the power drive module 40 stops driving the power device 200. Thus, through dual protection of software and hardware, the transmission of waves is quickly stopped when the voltage is undervoltage, achieving fast and reliable protection for the power device.

[0040] Among them, the voltage detection module 10 is configured to output an undervoltage detection result when the driving power is less than a preset threshold, the main control module 20 is configured to stop outputting the first control signal in response to the undervoltage detection result, and the level conversion module 30 is configured to stop level conversion and output of the first control signal in response to the undervoltage detection result, so that the power drive module 40 stops driving the power device 200.

[0041] The undervoltage detection result indicates that the drive power supply signal is undervoltage (the drive power supply is less than a preset threshold). For example, the undervoltage detection result can be a high level, such as 5V.

[0042] The preset threshold can be set according to requirements. For example, if the driving power supply is 15V, the preset threshold can be set to 10.8V, 10V, etc. This application embodiment does not limit this.

[0043] Specifically, the voltage detection module 10 is used to detect the voltage of the drive power supply at the drive power supply terminal and obtain the detection result. The detection result may include normal voltage (e.g., low level) or undervoltage (e.g., high level). The detection result can be simultaneously sent to the main control module 20 and the level conversion module 30. When the detection result is that the drive power supply is undervoltage, the main control module 20 can stop the wave generation through software control, and the level conversion module 30 can stop the level conversion and output of the first control signal through hardware circuitry, so that the power drive module 40 stops driving the power device 200.

[0044] In other words, since the detection results are simultaneously sent to the main control module 20 and the level conversion module 30, when the drive power supply is undervoltage, both the software (the software logic of the main control module 20 is to not generate a waveform upon receiving the undervoltage detection result, i.e., to stop outputting PWM1) and the hardware (the level conversion module 30 does not work when it receives the undervoltage detection result, i.e., to stop level conversion and outputting PWM1, i.e., to stop generating PWM2) can provide protection simultaneously. Through this dual protection of software and hardware, the generation of waveforms can be quickly stopped when undervoltage occurs (the generation of PWM1 is stopped in software and the generation of PWM2 is stopped in hardware), thus achieving fast and reliable protection for the power device 200.

[0045] For example, when the power supply (drive power supply at the drive power supply terminal) of the power drive module 40 (such as the drive chip 41) is abnormal, if it still receives the operating level from the level conversion module 30 (such as the tri-state buffer 31), the drive signal (PWM3) sent due to the abnormal power supply will not be able to keep the power device 200 completely in the on or off state, which may result in damage to the power device. However, the undervoltage protection circuit of the drive power supply provided in this application embodiment can detect the drive power supply in time, and can stop the machine in time if there is an abnormality in the drive power supply.

[0046] According to the undervoltage protection circuit 100 of the driving power supply provided in the embodiments of this application, the undervoltage protection circuit 100 may include a voltage detection module 10, a main control module 20, a level conversion module 30, and a power drive module 40. The input terminal of the voltage detection module 10 is electrically connected to the driving power supply terminal and is used to detect the driving power supply. It can output a corresponding detection result (which can be called the undervoltage detection result) when the driving power supply is below a preset threshold (undervoltage). The output terminal of the voltage detection module 10 is electrically connected to the input terminal of the main control module 20 and the control terminal (or enable terminal) of the level conversion module 30, respectively. That is, the undervoltage detection result can be simultaneously notified to the enable terminals of both the main control module 20 and the level conversion module 30. The software logic in the main control module 20 is to not transmit a waveform upon receiving the undervoltage detection result, that is, not to output the first control signal (such as pulse width modulation waveform PWM1) to the input terminal of the level conversion module 30, so that the level conversion module 30 cannot transmit a waveform. Wave transmission can be stopped in software to achieve protection of the power device. Meanwhile, the control terminal of the level conversion module 30 does not operate when it receives the undervoltage detection result, therefore it cannot perform level conversion and output the first control signal. Wave transmission can be stopped in hardware to protect the power device. The first input terminal of the power drive module 40 is electrically connected to the output terminal of the level conversion module 30, the second input terminal of the power drive module 40 is electrically connected to the drive power supply terminal, and the output terminal of the power drive module 40 is electrically connected to the power device. Therefore, when the level conversion module 30 is not transmitting waves, the power drive module 40 does not drive the power device. This dual hardware and software protection quickly stops wave transmission in the event of undervoltage, achieving rapid and reliable protection for the power device.

[0047] The voltage detection module 10 in the undervoltage protection circuit of the driving power supply provided in the embodiments of this application is described below.

[0048] Figure 2 This is another schematic diagram of the undervoltage protection circuit of the driving power supply provided in the embodiments of this application.

[0049] In some embodiments, such as Figure 2 As shown, the voltage detection module 10 may include a voltage regulator module 11, an isolation device 12, and a first resistor 13.

[0050] The voltage regulator module 11 and the first side of the isolation device 12 are connected in series between the drive power supply terminal and the first ground terminal (denoted as GND1).

[0051] Among them, the voltage regulator module 11 is used to determine the specific value of the preset threshold.

[0052] The first side of the isolation device 12 can also be referred to as the primary side or input side. The isolation device 12 may include an optocoupler, a relay, a transformer, etc. For example, an optocoupler can be used as the isolation device 12, and the light-emitting side of the optocoupler can be used as the first side of the isolation device 12. Compared with relays and transformers, optocouplers are less expensive and smaller in size.

[0053] The first ground terminal (GND1) is electrically connected to the drive power supply terminal and can be called high voltage ground.

[0054] The first end of the first resistor 13 is electrically connected to the reference power supply (e.g., 5V), and the second end of the first resistor 13 serves as the output of the voltage detection module 10.

[0055] The second side of the isolation device 12 is connected in series between the second terminal of the first resistor and the second ground terminal (denoted as GND2).

[0056] The second side of the isolation device 12 can also be called the secondary side or the output side.

[0057] The second ground terminal (GND2) is electrically connected to the reference power supply terminal and can be referred to as low-voltage ground.

[0058] For example, the driving power supply at the driving power supply end can be 15V, and the reference power supply at the reference power supply end can be 5V. When the driving power supply is greater than or equal to a preset threshold (e.g., 10.8V), the first side of the isolation device is turned on (e.g., the light-emitting diode inside the optocoupler emits light), and the second side of the isolation device is turned on (e.g., the transistor inside the optocoupler turns on in response to the light signal). After the second side of the isolation device 12 is turned on, the reference power supply (5V) and the second ground terminal (GND2) can be electrically connected through the first resistor 13 and the second side of the isolation device 12. The second end of the first resistor 13 is pulled to a low level (close to GND2). The second end of the first resistor 13 serves as the output terminal of the voltage detection module 10. Therefore, the output of the voltage detection module 10 is low (close to GND2), and the low level is the undervoltage detection result. The output terminal of the voltage detection module 10 is electrically connected to the input terminal of the main control module 20 and the control terminal (or enable terminal) of the level conversion module 30, respectively. That is, the undervoltage detection result can be simultaneously notified to the main control module 20 and the level conversion module 30. The software logic in the main control module 20 prevents the transmission of a waveform upon receiving an undervoltage detection result. Specifically, it prevents the output of the first control signal (such as pulse width modulation waveform PWM1) to the input of the level conversion module 30, thus preventing the level conversion module 30 from transmitting a waveform. This can be achieved by stopping waveform transmission via software, protecting the power device. Simultaneously, the control terminal of the level conversion module 30 remains inactive upon receiving an undervoltage detection result, preventing the level conversion and output of the first control signal. This can be achieved by stopping waveform transmission via hardware, protecting the power device. When the level conversion module 30 is not transmitting a waveform, the power drive module 40 stops driving the power device 200. This dual hardware and software protection ensures rapid and reliable protection of the power device by quickly stopping waveform transmission in the event of undervoltage.

[0059] The fact that the driving power supply at the driving power supply terminal is 15V and the reference power supply at the reference power supply terminal is 5V is merely exemplary and not intended to limit this application. In other embodiments, the driving power supply at the driving power supply terminal and the reference power supply at the reference power supply terminal may have other values.

[0060] The voltage detection module 10 in the drive power supply undervoltage protection circuit 100 provided in this application embodiment sets a preset threshold through the voltage regulation module 11 and achieves electrical isolation using the isolation device 12 (such as an optocoupler). When the drive power supply is undervoltage, it outputs a low-level signal. This signal can simultaneously notify the main control module 20 and the level conversion module 30. The main control module 20 stops transmitting waves at the software level, and the level conversion module 30 stops transmitting waves at the hardware level, thereby causing the power drive module 40 to stop driving the power device 200. Through the dual protection of software and hardware, the transmission of waves is quickly stopped when undervoltage occurs, thus achieving fast and reliable protection for the power device.

[0061] Figure 3This is another schematic diagram of the undervoltage protection circuit of the driving power supply provided in the embodiments of this application.

[0062] In some embodiments, such as Figure 3 As shown, the voltage regulator module 11 may include a second resistor 111 and a Zener diode 112.

[0063] The second resistor 111, the Zener diode 112, and the first side of the isolation device 12 are connected in series between the drive power supply terminal and the first ground terminal GND1.

[0064] In other words, in the voltage detection module 10, the first side of the isolation device 12 (such as the input side of the optocoupler) is connected in series with a pull-up resistor (second resistor 111) and a Zener diode 112. By selecting appropriate resistance values ​​and Zener diode voltage, the current (denoted as IF) on the first side of the isolation device 12 can be determined.

[0065] The voltage detected in the voltage detection module 10 is the power supply of the power drive module 40 (the drive power supply at the drive power supply end), for example, 15V. The first side of the isolation device 12 is grounded (GND1) with the power drive module 40 (such as the drive chip 41).

[0066] For example, in the voltage detection module 10, the second side of the isolation device 12 is connected to a pull-up current limiting resistor (first resistor 13). Selecting an appropriate resistance value of the first resistor 13 can limit the current on the second side of the isolation device 12 (such as the current of the transistor in the optocoupler). This current can be denoted as IC to meet the derating factor of the current transfer ratio (which can be denoted as CTR) of the isolation device 12 under operating conditions. CTR = primary current IC / secondary current IF × 100%.

[0067] The components selected and calculated for the voltage regulator module 11 are as follows: Zener diode 112 selection calculation: Taking a 15V driving power supply and an optocoupler with isolation device 12 as an example, considering the high temperature operating conditions, the maximum forward voltage on the input side of the optocoupler is between 0.8V and 1.6V. A 10V Zener diode 112 can be selected. When the driving power supply is lower than 10.8V, the optocoupler does not work, and the secondary voltage is pulled up to a high level (e.g., 5V) by the reference power supply terminal (e.g., 5V).

[0068] The calculation for selecting the second resistor 111: Under normal operation, the voltage across the second resistor 111 is approximately 4V. A 1kΩ resistor can be selected for the second resistor 111 to ensure that the input current IF of the optocoupler is approximately 4mA. A 4mA IF current is the typical operating current of the primary diode of the optocoupler, ensuring normal operation of the optocoupler while preventing excessive current from damaging the device.

[0069] In one example, the inventors discovered that under high-temperature conditions, when the input current IF of the optocoupler is 4mA, the current transfer ratio (CTR) of the optocoupler (which can be simply understood as the current amplification factor) is inversely proportional to the temperature and also inversely proportional to the output current IF of the optocoupler. The derating factor can be obtained from the datasheet.

[0070] It should be noted that in the voltage detection module 10, the second side of the isolation device 12 is connected to a pull-up current limiting resistor (first resistor 13). Selecting an appropriate resistance value for the first resistor 13 can limit the current on the second side of the isolation device 12 (such as the current of the transistor in the optocoupler). This current can be denoted as IC, in order to meet the derating factor of the current transfer ratio (which can be denoted as CTR) of the isolation device 12 under operating conditions. CTR = primary current IC / secondary current IF × 100%.

[0071] Taking an optocoupler with a current transfer ratio (CTR) derating factor of 0.6 * 0.7 = 0.42 as an example, where 0.6 and 0.7 are the derating factors for temperature and current transfer ratio (IF), respectively, the specific values ​​need to be determined according to the datasheet. Assuming the optocoupler's factory-set CTR is at least 1.3 (i.e., the current amplification factor is at least 1.3 times), then in actual use under high-temperature conditions, the minimum CTR is 1.3 * 0.42 = 0.546 times. Therefore, the maximum current IC that the secondary transistor of the optocoupler can amplify is the input current 4mA * current transfer ratio 0.546 = 2.184mA. The actual IC needs to be less than 2.184mA to ensure that the secondary transistor of the optocoupler operates stably in the saturation region. Therefore, the pull-up current-limiting resistor (first resistor 13) needs to be designed to be 4.7kΩ, so that IC = reference power supply 5V / 4700Ω ≈ 1mA < 2.184mA, to ensure that the secondary transistor of the optocoupler operates stably in the saturation region. This ensures that the optocoupler can still meet the circuit design requirements under extreme conditions (such as high temperature).

[0072] In this embodiment, a voltage regulator module 11 is formed by a second resistor 111 and a Zener diode 112. The primary-side operating current IF of the isolation device (such as an optocoupler) is precisely set. Based on the inverse relationship between the current transfer ratio CTR of the isolation module 12 under high-temperature conditions and the temperature and the secondary-side current IC of the isolation module 12 (such as the optocoupler), the derating factor is looked up in the datasheet. The actual current transfer ratio under high-temperature conditions is calculated based on the derating factor. Then, the resistance value of the pull-up current limiting resistor (second resistor 111) is reasonably designed. The derating design ensures the normal operation of the isolation device 12 (such as the stable operation of the secondary-side transistor of the optocoupler in the saturation region), improves the reliability of the circuit under extreme conditions, and effectively ensures the accuracy and stability of the undervoltage protection of the drive power supply.

[0073] Figure 4This is another schematic diagram of the undervoltage protection circuit of the driving power supply provided in the embodiments of this application.

[0074] In some embodiments, such as Figure 4 As shown, the voltage detection module 10 may also include a third resistor 14.

[0075] The third resistor 14 is connected in parallel with the first side of the isolation device 12.

[0076] The third resistor 14 is connected in parallel with the first side (such as the primary side of the optocoupler) of the isolation device 12 to discharge the energy of the parasitic capacitance inside the first side (such as the primary side of the optocoupler) of the isolation device 12, and to ensure the normal transmission of the signal on the first side (such as the primary side of the optocoupler) of the isolation device 12.

[0077] For example, the third resistor 14 is selected in the kΩ range. Therefore, for a voltage of about 1V across the LED on the primary side of the optocoupler, the current in the third resistor 14 is very small compared to the primary side current IF (4mA) of the optocoupler and can be ignored. The third resistor 14 is used to limit the voltage across the LED on the primary side of the optocoupler to prevent the LED from being damaged by excessive voltage, while its current has a negligible impact on the overall circuit.

[0078] In this embodiment, the third resistor 14 added to the voltage detection module 10 is connected in parallel with the first side of the isolation device 12. This can both release the energy of the parasitic capacitance inside the isolation device 12 (such as an optocoupler) to ensure stable signal transmission and limit the voltage of the primary-side light-emitting diode of the optocoupler to prevent overvoltage damage. Moreover, its kΩ-level resistance value makes the shunt current extremely small (far lower than the primary-side operating current). Without affecting the normal function of the circuit, it significantly improves the reliability and anti-interference capability of the undervoltage protection circuit.

[0079] Figure 5 This is another schematic diagram of the undervoltage protection circuit of the driving power supply provided in the embodiments of this application.

[0080] In some embodiments, such as Figure 5 As shown, the voltage detection module 10 may also include a fourth resistor 15 and a capacitor 16.

[0081] The first end of the fourth resistor 15 is electrically connected to the second end of the first resistor 13, and its second end serves as the output end of the voltage detection module 10.

[0082] Capacitor 16 is electrically connected between the second terminal of the fourth resistor 15 and the second ground terminal GND2.

[0083] The fourth resistor 15 and capacitor 16 can constitute a filter module for signal filtering. Of course, other types of filter modules can also be used in other embodiments.

[0084] In this embodiment, the voltage detection module 10 forms a filter module through the fourth resistor 15 and the capacitor 16, which can effectively filter out high-frequency noise and interference glitches in the output signal and avoid false detection. At the same time, its simple RC structure has advantages in cost and size, and improves the anti-interference ability of the circuit under complex working conditions.

[0085] Figure 6 This is another schematic diagram of the undervoltage protection circuit of the driving power supply provided in the embodiments of this application.

[0086] In some embodiments, such as Figure 6 As shown, the isolation device 12 may include an optocoupler.

[0087] The first side of the optocoupler (also known as the primary side or input side) includes a light-emitting diode 121, and the second side of the optocoupler (also known as the secondary side or output side) includes a transistor 122.

[0088] Among them, the isolation device 12 uses an optocoupler, which can reduce the size and cost compared to isolation devices such as relays and transformers.

[0089] For example, when the drive power supply is normal, the primary side of the optocoupler is on, the secondary side transistor operates in the saturation region, and the output signal of the voltage detection module 10 is reliably pulled to ground (close to GND1). That is, the voltage detection module 10 outputs a low level (i.e., a normal detection result, indicating that the drive power supply is normal). The low level is simultaneously given to the enable pins of the main control module 20 (such as the main control chip 21) and the level conversion module 30 (such as the tri-state buffer 31). The main control module 20 (such as the main control chip 21) determines through software that there is no fault and sends the first control signal PWM1 to the level conversion module 30 (such as the tri-state buffer 31). The enable pin of 0 (such as the tri-state buffer 31) is active low. After receiving the first control signal PWM1 from the main control module 20 (such as the main control chip 21), it converts the first control signal PWM1 into a working level that the power drive module 40 (such as the driver chip 41) can receive, that is, into the second control signal PWM2. The power supply of the power drive module 40 (such as the driver chip 41) (the drive power supply at the drive power supply end) is normal (such as 15V), and the received working level is also normal (also 15V). Therefore, it can send a drive signal (the third control signal PWM3) to enable the power device 200 to turn on normally. Among them, the duty cycle of PWM1~PWM3 is the same but the voltage amplitude is different.

[0090] For example, when the driving power supply is undervoltage, the primary side of the optocoupler cannot conduct, the secondary side transistor cannot conduct, and the output signal of the voltage detection module 10 is pulled high by the reference power supply to obtain a high level (that is, the undervoltage detection result, which indicates that the driving power supply is undervoltage). The high level is simultaneously given to the enable pin of the main control module 20 (such as the main control chip 21) and the level conversion module 30 (such as the tri-state buffer 31). The main control module 20 stops outputting the first control signal in response to the undervoltage detection result, and the level conversion module 30 stops the level conversion and output of the first control signal in response to the undervoltage detection result, so that the power drive module 40 stops driving the power device 200.

[0091] This application uses an optocoupler as an isolation device, which significantly reduces circuit size and cost while achieving electrical isolation. When the drive power supply is normal, the secondary transistor of the optocoupler is saturated and conducts, causing the output terminal to stably output a low level. The main control module and the level conversion module then work together to output a normal drive signal, ensuring that the power device is turned on and off normally. When the drive power supply is undervoltage, the secondary side of the optocoupler is cut off, causing the output terminal to switch to a high level. The main control module and the level conversion module immediately stop signal output and quickly cut off the drive of the power device. The high-low level conversion of the optocoupler achieves accurate detection and rapid protection of the undervoltage state, effectively improving the reliability and safety of the circuit.

[0092] Figure 7 This is another schematic diagram of the undervoltage protection circuit of the driving power supply provided in the embodiments of this application.

[0093] In some embodiments, such as Figure 7 As shown, the power drive module 40 may include a drive chip 41, which is electrically connected to the first ground terminal GND1.

[0094] The first side of the isolation device 12 and the power drive module 40 can share a high voltage ground (GND1), and the drive power supply 15V is a high voltage.

[0095] In this embodiment, the power drive module 40 (such as the drive chip 41) and the first side of the isolation device 12 share a common ground (GND1). The common ground design ensures the potential synchronization between the primary side of the isolation device 12 and the power drive module 40.

[0096] In some embodiments, see [link to relevant documentation]. Figure 7 The main control module 20 may include a main control chip 21, which is electrically connected to the second ground terminal GND2.

[0097] Among them, the main control chip 21 can use a digital signal processor (DSP) to perform high-speed digital signal processing.

[0098] This embodiment uses a main control chip 21 as the main control module 20, fully leveraging the high-speed digital signal processing capabilities of the main control chip 21 (such as a DSP) to significantly improve the response speed of undervoltage detection. Furthermore, the physical potential separation between the high-voltage and low-voltage grounds effectively blocks electromagnetic interference and noise coupling from the high-voltage side to the low-voltage control loop, ensuring high immunity and reliability of the circuit.

[0099] In some embodiments, see [link to relevant documentation]. Figure 7 The level conversion module 30 may include a tri-state buffer 31 (capable of outputting high level, low level, and high impedance state).

[0100] The enable terminal of the tri-state buffer 31 is electrically connected to the output terminal of the voltage detection module 10, the input terminal of the tri-state buffer 31 is electrically connected to the output terminal of the main control module 20, and the output terminal of the tri-state buffer 31 is electrically connected to the first input terminal of the power drive module 40.

[0101] The working principle of the tri-state buffer 31 is as follows: when the enable terminal receives an enable signal (such as a low level), it converts the PWM1 at the input terminal into PWM2 and outputs it; when the enable terminal is a non-enable signal (such as a high level), it outputs a high-impedance state.

[0102] This embodiment employs a tri-state buffer 31 to construct a level conversion module 30. The tri-state buffer 31 can output high, low, and high impedance states. In the enabled state, it outputs high and low levels of PWM2, while in the disabled state, the output is in a high impedance state. Specifically, when the voltage detection module outputs an enable signal (such as a low level), the tri-state buffer 31 converts the first control signal PWM1 to obtain PWM2 and outputs it to the driver chip 41, ensuring effective execution of the control command. In the disabled state (enable terminal is high level), the tri-state buffer 31 can output a high impedance state, completely cutting off the signal path to prevent malfunction of the driver chip 41. This approach utilizes the level conversion capability of the tri-state buffer to adapt to different voltage domains and effectively prevents high-voltage side backflow interference through the high impedance isolation function, significantly improving the reliability and anti-interference capability of the drive power supply undervoltage protection system.

[0103] The following describes the specific working process when the drive power supply is normal.

[0104] In some embodiments, see Figures 1 to 7 .

[0105] The voltage detection module 10 is configured to output a normal detection result when the driving power supply is less than a preset threshold. The main control module 20 outputs a first control signal in response to the normal detection result. The level conversion module 30 converts the first control signal PWM1 to obtain a second control signal PWM2 in response to the normal detection result and outputs it. The power drive module 40 converts the second control signal PWM2 to obtain a third control signal PWM3 according to the driving power supply and drives the power device according to the third control signal PWM3.

[0106] Among them, the first control signal PWM1, the second control signal PWM2, and the third control signal PWM3 have the same duty cycle but different voltage amplitudes.

[0107] For example, such as Figure 7 As shown, the output terminal of the voltage detection module 10 can be marked as Fault.

[0108] If the drive power supply is normal, the Fault signal at the output terminal of the voltage detection module 10 will be low. This low level simultaneously enables the main control chip and the tri-state buffer. The main control chip responds to this low level by outputting the first control signal PWM1 according to its internal logic. Simultaneously, the tri-state buffer 31 is enabled. When the tri-state buffer 31 receives the first control signal PWM1 from the main control chip 21, it converts it into a working level (the second control signal PWM2) that the drive chip 41 can receive and outputs it to the drive chip 41. The drive chip 41 generates a third control signal PWM3 based on the drive power supply to regulate the operation of the power devices. Therefore, when the drive power supply is normal, the optocoupler operates normally, the secondary transistor of the optocoupler is saturated, the Fault signal is reliably pulled low, and the entire system operates normally.

[0109] When the drive power supply is abnormal (below the design value), the secondary transistor of the optocoupler immediately exits the saturation region, the Fault signal is pulled high, and the Fault signal is reported to the main control chip 21. The main control chip 21 then stops transmitting waveforms (stops transmitting PWM1). At the same time, it directly shuts down the enable pin of the tri-state buffer 31 (directly cutting off the enable pin of the tri-state buffer stops transmitting waveforms, i.e., stops transmitting PWM2). The drive chip 41 stops working, and the entire machine shuts down, thereby protecting the power devices, the motors connected to the power devices, and the control chip from damage. In this embodiment, the tri-state buffer is stopped directly through software judgment, resulting in a faster hardware response (the tri-state buffer responds faster). Furthermore, it can stop transmitting waveforms in software when the hardware fails, providing a double protection effect of hardware and software. At the same time, the cost of the hardware design is lower than that of selecting highly integrated drive chips, isolation operational amplifiers, and comparators.

[0110] This embodiment of the application can output a detection result indicating that the driving power supply is normal when the power supply is normal via a voltage detection module. This triggers the main control module to generate a first control signal PWM1, which is then converted by the level conversion module 30 into a second control signal PWM2 adapted to the voltage domain of the power drive module 40. Finally, the power drive module 40 converts this signal into a third control signal PWM3 to drive the power device. By maintaining a consistent duty cycle, control accuracy is ensured. At the same time, multi-level level conversion isolates different voltage domains, effectively avoiding interference from the high-voltage side to the low-voltage control circuit. This significantly improves the system's noise immunity and signal transmission stability, ensuring accurate driving of the power device in complex electromagnetic environments.

[0111] It should be understood that in the embodiments of this application, "B corresponding to A" means that B is associated with A, and B can be determined based on A. However, it should also be understood that determining B based on A does not mean that B is determined solely based on A; B can also be determined based on A and / or other information.

[0112] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An undervoltage protection circuit for a drive power supply, characterized in that, include: The voltage detection module has its input terminal electrically connected to the drive power supply terminal; The main control module has its input terminal electrically connected to the output terminal of the voltage detection module; A level conversion module, the enable terminal of which is electrically connected to the output terminal of the voltage detection module, and the input terminal of which is electrically connected to the output terminal of the main control module; The power drive module has a first input terminal electrically connected to the output terminal of the level conversion module, a second input terminal electrically connected to the drive power supply terminal, and an output terminal electrically connected to the power device. The voltage detection module is configured to output an undervoltage detection result when the driving power supply is less than a preset threshold. The main control module is configured to stop outputting a first control signal in response to the undervoltage detection result. The level conversion module is configured to stop level conversion and output of the first control signal in response to the undervoltage detection result, so that the power drive module stops driving the power device.

2. The undervoltage protection circuit according to claim 1, characterized in that, The voltage detection module includes a voltage regulator module, an isolation device, and a first resistor: The voltage regulator module and the first side of the isolation device are connected in series between the drive power supply terminal and the first ground terminal; The first end of the first resistor is electrically connected to the reference power supply terminal, and the second end of the first resistor serves as the output terminal of the voltage detection module. The second side of the isolation device is connected in series between the second terminal of the first resistor and the second ground terminal.

3. The undervoltage protection circuit according to claim 2, characterized in that, The voltage regulator module includes a second resistor and a Zener diode; The second resistor, the Zener diode, and the first side of the isolation device are connected in series between the drive power supply terminal and the first ground terminal.

4. The undervoltage protection circuit according to claim 2, characterized in that, The voltage detection module further includes: The third resistor is connected in parallel with the first side of the isolation device.

5. The undervoltage protection circuit according to claim 2, characterized in that, The voltage detection module also includes a fourth resistor and a capacitor: The fourth resistor has its first end electrically connected to the second end of the first resistor, and its second end serves as the output terminal of the voltage detection module. The capacitor is electrically connected between the second terminal of the fourth resistor and the second ground terminal.

6. The undervoltage protection circuit according to claim 2, characterized in that, The isolation device includes an optocoupler.

7. The undervoltage protection circuit according to claim 2, characterized in that, The power drive module includes a drive chip, which is electrically connected to a first ground terminal.

8. The undervoltage protection circuit according to claim 2, characterized in that, The main control module includes a main control chip, which is electrically connected to a second ground terminal.

9. The undervoltage protection circuit according to claim 1, characterized in that, The level conversion module includes: The three-state buffer has its enable terminal electrically connected to the output terminal of the voltage detection module, its input terminal electrically connected to the output terminal of the main control module, and its output terminal electrically connected to the first input terminal of the power drive module.

10. The undervoltage protection circuit according to any one of claims 1 to 9, characterized in that, The voltage detection module is configured to output a normal detection result when the driving power supply is less than the preset threshold. The main control module outputs a first control signal in response to the normal detection result. The level conversion module converts the first control signal to obtain a second control signal in response to the normal detection result and outputs it. The power drive module converts the second control signal to obtain a third control signal according to the driving power supply and drives the power device according to the third control signal.

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