A method for increasing the output current of a power switching device

Abstract

The present invention belongs to the field of industrial control technology, relates to the application scenario of motor motion control, and specifically provides a method for improving the output current of a power switching device, so as to enhance the current output capacity of the power switching device, maximize the working potential, and thus reduce the system cost and the requirements for system heat dissipation design; the present invention conducts a detailed study on the working characteristics of the power switching device, creatively proposes to use the feedback speed of the motor encoder as a characterization value, and further proposes switching decision conditions for the switching frequency based on this characterization value, including down-frequency conditions and up-frequency conditions. During the motor motion control process, the high-frequency and low-frequency switching of the switching frequency is automatically completed. On the premise of ensuring the motor control performance, the current output capacity of the power switching device is effectively enhanced, the working potential of the power switching device is maximized, which is beneficial to reducing the system cost and the requirements for system heat dissipation design.

Description

Technical Field

[0001] The present invention belongs to the technical field of industrial control, relates to the application scenario of motor motion control, and specifically provides a method for increasing the output current of a power switch device. Background Art

[0002] Power switch devices are widely used in the fields of power supply, wind power, solar energy, electric vehicles, and industrial automation. As the core devices in these fields, if the capacity of the power switch device is selected too large, it will cause waste, and the maximum efficiency of the device cannot be exerted. Moreover, larger-capacity devices will bring higher system costs; while if the capacity of the power switch device is selected too small, it will cause the device to work under large current conditions, resulting in an increase in the junction temperature, which may bring system risks and even cause the power switch device to explode and the system to fail. Therefore, how to optimize the use of power switch devices has become the research focus of the present invention. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for increasing the output current of a power switch device, so as to improve the current output ability of the power switch device, maximize the working potential, and thus reduce the system cost and the requirements for system heat dissipation design. The present invention conducts a detailed study on the working characteristics of the power switch device, and creatively proposes to use the feedback speed of the motor encoder as a characterization value. Further, based on this characterization value, switching decision conditions for the switching frequency are proposed, including a down-frequency condition and an up-frequency condition. During the motor motion control process, the high and low frequency switching of the switching frequency is automatically completed. On the premise of ensuring the motor control performance, the current output ability of the power switch device is effectively improved, the working potential of the power switch device is maximized, which is beneficial to reducing the system cost and the requirements for system heat dissipation design.

[0004] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0005] A method for increasing the output current of a power switch device, comprising the following steps:

[0006] Step 1. System initialization, initializing the switching frequency of the power switch device in the PWM peripheral module of the MCU to the high-frequency state;

[0007] Step 2. The control platform enters the enable control state, receives a speed command or a position command, and the PWM peripheral module sends a PWM signal to perform speed control or position control on the motor;

[0008] Step 3. Real-time detect the feedback speed of the motor encoder, and determine whether the feedback speed reaches the down-frequency condition. If it reaches the down-frequency condition, execute Step 4; otherwise, maintain the current state for motor control;

[0009] Step 4. Keep the control platform in the enabled control state. Configure the PWM peripheral module by the MCU to switch the switching frequency of the power switch device to the low-frequency state. At the same time, the control platform matches the control parameters according to the switching frequency.

[0010] Step 5. Continuously detect the feedback speed of the motor encoder in real time, and determine whether the feedback speed reaches the frequency increase condition. If it reaches the frequency increase condition, execute Step 6; otherwise, maintain the current state for motor control.

[0011] Step 6. Keep the control platform in the enabled control state. Configure the PWM peripheral module by the MCU to switch the switching frequency of the power switch device to the high-frequency state. At the same time, the control platform matches the control parameters according to the switching frequency.

[0012] Step 7. The control platform continuously controls the motor in the enabled control state until it receives the next enable command to end the working state.

[0013] Further, in Step 1, the high-frequency state is specifically 12 kHz.

[0014] Further, in Step 3, the frequency reduction condition is specifically: the feedback speed is lower than 5 revolutions per minute and the duration is greater than 3 seconds.

[0015] Further, in Step 4, the low-frequency state is specifically 6 kHz.

[0016] Further, in Step 4, the adjustment formula for the control parameters is specifically:

[0017] kp1 = (k1 / k2) × kp2, ki1 = (k1 / k2) × ki2;

[0018] where kp1 is the low-frequency proportional control parameter of the current loop, kp2 is the high-frequency proportional control parameter of the current loop, k1 is the switching frequency in the low-frequency state, k2 is the switching frequency in the high-frequency state; ki1 is the low-frequency integral control parameter of the current loop, and ki2 is the high-frequency integral control parameter of the current loop.

[0019] Further, in Step 6, the frequency increase condition is specifically: the feedback speed is higher than or equal to 5 revolutions per minute.

[0020] Further, in Step 6, the adjustment formula for the control parameters is specifically:

[0021] kp2 = (k2 / k1) × kp1, ki2 = (k1 / k2) × ki1;

[0022] where kp1 is the low-frequency proportional control parameter of the current loop, kp2 is the high-frequency proportional control parameter of the current loop, k1 is the switching frequency in the low-frequency state, k2 is the switching frequency in the high-frequency state; ki1 is the low-frequency integral control parameter of the current loop, and ki2 is the high-frequency integral control parameter of the current loop.

[0023] Based on the above technical solution, the beneficial effects of the present invention are as follows:

[0024] The present invention provides a method for increasing the output current of a power switching device. Through a detailed study of the operating characteristics of the power switching device, it creatively proposes using the feedback speed of the motor encoder as a characterization value, and further proposes switching decision conditions for the switching frequency based on this characterization value, including down-frequency conditions and up-frequency conditions. During the motor motion control process, the PWM frequency (the operating frequency of the switching device) is initialized to a high frequency (12 kHz), and the servo driver executes the motor control process, which is the same as the conventional control process. Moreover, the feedback speed of the motor encoder is monitored in real time. When the set down-frequency condition is met, that is, the feedback speed is lower than 5 RPM and the duration is greater than 3 seconds, the PWM peripheral module configuration is modified to switch the PWM frequency to a low frequency (6 kHz), and the current loop control parameters are modified to make the motor enter low-frequency control, effectively reducing the case temperature of the power device, thereby improving the current output capacity of the power switching device and further adapting to a larger load. At the same time, when the feedback speed is higher than 5 RPM, that is, the predetermined up-frequency condition is reached, the PWM peripheral configuration is modified again to switch the PWM frequency to a high frequency (12 kHz), and the control parameters of the current control loop are modified to make the motor enter high-frequency control. Based on this, the high-low frequency switching is automatically completed during the entire motor motion control process. On the premise of ensuring the motor control performance, the current output capacity of the power switching device is effectively improved, maximizing the working potential of the power switching device, which is beneficial to reducing the system cost and the system heat dissipation design requirements. Description of the Drawings

[0025] Figure 1 It is a PWM waveform diagram output by the MCU during the process of the switching frequency of the power switching device switching from high frequency to low frequency.

[0026] Figure 2 It is a PWM waveform diagram output by the MCU during the process of the switching frequency of the power switching device switching from low frequency to high frequency.

[0027] Figure 3 It is a flow schematic diagram of the method for increasing the output current of the power switching device provided by the present invention. Detailed Embodiments

[0028] To make the objectives, technical solutions, and beneficial effects of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the drawings and embodiments.

[0029] The present invention provides a method for increasing the output current of a power switching device. In terms of the working principle, the data sheet of the power switching device will give the nominal current, which is an instantaneous current rather than the rated current of the power switching device. Since the rated current of the power switching device depends on the heat dissipation of the system and is related to the system design, if the system has better heat dissipation, the rated current of the power switching device can be increased. Therefore, the data sheet does not give the rated current of the power switching device. However, it can be seen from the data sheet of the power switching device that the rated current of the device is related to the case temperature. The rated current is defined at a given case temperature. The lower the case temperature, the greater the output current of the power switching device. The specific relationship is expressed as: T vimax =T c + R thjc ×(I cn ×V ce_sat ), where T vimax is the maximum allowable value of the junction temperature of the power switching device, usually a fixed value, T vimax = 175 °C; T c is the case temperature of the power switching device, R thjc is the junction-case resistance of the power switching device, I cn is the rated collector current of the power switching device; V ce_sat is the collector-emitter saturation voltage of the power switching device, usually also a fixed value. Thus, reducing the case temperature T c can increase the rated collector current I cn . The direct way to reduce the case temperature is to reduce the switching loss. Reducing the switching frequency can reduce the switching loss per unit time, but reducing the switching frequency will affect the system control performance. Therefore, it is necessary to fully consider the working characteristics of the power switching device, set the frequency switching conditions, and reasonably reduce the switching frequency of the device on the premise of meeting the system control performance to achieve the purpose of reducing the case temperature T c and improve the current output ability of the power switching device.

[0030] Through testing, as Figure 1 shows the PWM waveform output by the MCU during the process of the switching frequency of the power switching device switching from high frequency to low frequency, and as Figure 2 shows the PWM waveform output by the MCU during the process of the switching frequency of the power switching device switching from low frequency to high frequency; it can be seen from the figure that both the high-low frequency switching processes are smoothly switched, and no abnormal situation where the upper and lower bridge arms are both open occurs. In motor motion control, a higher switching frequency means a higher control bandwidth, which also means a faster response speed, and thus higher control performance. However, a higher switching frequency will also bring greater switching loss, thereby reducing the current output ability of the power switching device.

[0031] In summary, the present invention uses the feedback speed of the encoder of the motor as a characterization value, and proposes frequency switching conditions based on this characterization value, including up-frequency conditions and down-frequency conditions; initializes the switching frequency of the power switch device to a high-frequency state to achieve high-performance motor control, and monitors the characterization value in real time. When the characterization value reaches the down-frequency condition, the switching frequency of the power switch device is switched to a low-frequency state, and the control parameters are adjusted accordingly, thereby reducing the switching loss and increasing the output current of the power switch device; on this basis, based on the method proposed by the present invention, the current output potential of the power switch device can be fully exerted, and the system cost and the system heat dissipation design requirements can be reduced.

[0032] Based on the above working principle, the present invention provides a specific embodiment. The flow of the method for increasing the output current of the power switch device is as Figure 3 shown, and specifically includes the following steps:

[0033] Step 1. System initialization. Initialize the switching frequency of the power switch device in the PWM (Pulse Width Modulation) peripheral module of the MCU (Microcontroller Unit) to a high-frequency state, specifically 12 kHz; at the same time, initialize the control parameters of the motor; and perform matching settings on the registers of the MCU to meet the requirements of motor control; The type of MCU is not limited. It can be a DSP (Digital Signal Processor) digital processor or an ARM (Advanced RISC Machine) chip. Both the DSP digital processor and the ARM chip are commonly used MCUs for power switch devices;

[0034] After the system initialization is completed, the control platform enters the ready state and waits to receive commands from the host computer or the main controller;

[0035] Step 2. The control platform enters the enable control state, receives the speed command or the position command, and sends a PWM signal by the PWM peripheral module to perform speed control or position control on the motor; The control platform usually receives the speed command or the position command issued by the host computer or the main controller through the bus communication method;

[0036] Step 3. Real-time detect the feedback speed of the encoder of the motor, and judge whether the feedback speed reaches the down-frequency condition. If it reaches the down-frequency condition, execute Step 4; otherwise, maintain the current state for motor control;

[0037] The down-frequency condition is specifically: the feedback speed is lower than 5 revolutions per minute and the duration is greater than 3 seconds. More specifically, only when the feedback speed is lower than 5 revolutions per minute and the duration of the feedback speed being lower than 5 revolutions per minute is greater than 3 seconds, the operating frequency of the power switch device is down-frequency processed;

[0038] The monitoring process of the feedback speed of the encoder is as follows: The MCU collects the position of the encoder in real time and calculates the speed of the motor based on the position information of the encoder;

[0039] Step 4. Keep the control platform in the enabled control state. The MCU configures the PWM peripheral module to switch the switching frequency of the power switch device to the low-frequency state, specifically 6 kHz. At the same time, the control platform matches the control parameters according to the switching frequency to make the control parameters adapt to the low-frequency state;

[0040] Since switching the switching frequency to the low-frequency state will cause the system bandwidth to decrease, it is necessary to match and adjust the corresponding current-loop control parameters, otherwise it may lead to abnormal control. The adjustment formula is specifically:

[0041] kp1=(k1 / k2)×kp2, ki1=(k1 / k2)×ki2;

[0042] Among them, kp1 is the current-loop low-frequency proportional control parameter, kp2 is the current-loop high-frequency proportional control parameter, k1 is the switching frequency in the low-frequency state, k2 is the switching frequency in the high-frequency state; ki1 is the current-loop low-frequency integral control parameter, ki2 is the current-loop high-frequency integral control parameter;

[0043] Step 5. Detect the feedback speed of the encoder of the motor in real time and determine whether the feedback speed reaches the frequency-increase condition. If it reaches the frequency-increase condition, execute Step 6; otherwise, maintain the current state for motor control;

[0044] The frequency-increase condition is specifically: the feedback speed is higher than or equal to 5 revolutions per minute. More specifically, only when the feedback speed is higher than or equal to 5 revolutions per minute, the working frequency of the power switch device is increased;

[0045] Step 6. Keep the control platform in the enabled control state. The MCU configures the PWM peripheral module to switch the switching frequency of the power switch device to the high-frequency state. At the same time, the control platform matches the control parameters according to the switching frequency to make the control parameters adapt to the high-frequency state. The adjustment formula is specifically:

[0046] kp2=(k2 / k1)×kp1, ki2=(k1 / k2)×ki1;

[0047] Among them, kp1 is the current-loop low-frequency proportional control parameter, kp2 is the current-loop high-frequency proportional control parameter, k1 is the switching frequency in the low-frequency state, k2 is the switching frequency in the high-frequency state; ki1 is the current-loop low-frequency integral control parameter, ki2 is the current-loop high-frequency integral control parameter;

[0048] Step 7. The control platform continuously controls the motor in the enabled control state until the next enable command is received, and then the working state ends; thus, in the motor motion control process of this embodiment, the effective output of the current of the power switch device is improved.

[0049] As described above, the above are only specific embodiments of the present invention. Any feature disclosed in this specification, unless specifically described, can be replaced by other equivalent or similar-purpose alternative features; all the features disclosed, or all the steps in any method or process, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A method for increasing the output current of a power switching device, characterized in that, It includes the following steps: Step 1. System initialization. Initialize the switching frequency of the power switch device in the PWM peripheral module of the MCU to the high-frequency state. Step 2. The control platform enters the enable control state, receives a speed command or a position command, and the PWM peripheral module sends a PWM signal to control the speed or position of the motor. Step 3. Continuously detect the feedback speed of the motor encoder, and determine whether the feedback speed reaches the down-frequency condition. If it reaches the down-frequency condition, execute Step 4; otherwise, maintain the current state for motor control. Step 4. The control platform maintains the enable control state. The MCU configures the PWM peripheral module to switch the switching frequency of the power switch device to the low-frequency state. At the same time, the control platform matches the control parameters according to the switching frequency. Step 5. Continuously detect the feedback speed of the motor encoder, and determine whether the feedback speed reaches the up-frequency condition. If it reaches the up-frequency condition, execute Step 6; otherwise, maintain the current state for motor control. Step 6. The control platform maintains the enable control state. The MCU configures the PWM peripheral module to switch the switching frequency of the power switch device to the high-frequency state. At the same time, the control platform matches the control parameters according to the switching frequency. Step 7. The control platform continuously controls the motor in the enable control state until it receives the next enable command and ends the working state.

2. The method for increasing the output current of a power switching device according to claim 1, characterized in that, In Step 1, the high-frequency state is specifically 12 kHz.

3. The method for increasing the output current of a power switching device according to claim 1, characterized in that In Step 3, the down-frequency condition is specifically: the feedback speed is lower than 5 revolutions per minute and the duration is greater than 3 seconds.

4. The method for increasing the output current of a power switching device according to claim 1, wherein In Step 4, the low-frequency state is specifically 6 kHz.

5. The method for increasing the output current of a power switching device according to claim 1, characterized in that, In Step 4, the adjustment formula for the control parameters is specifically: kp1 = (k1 / k2) × kp2, ki1 = (k1 / k2) × ki2; where kp1 is the low-frequency proportional control parameter of the current loop, kp2 is the high-frequency proportional control parameter of the current loop, k1 is the switching frequency in the low-frequency state, k2 is the switching frequency in the high-frequency state; ki1 is the low-frequency integral control parameter of the current loop, ki2 is the high-frequency integral control parameter of the current loop.

6. The method for increasing the output current of a power switching device according to claim 1, characterized in that, In Step 6, the up-frequency condition is specifically: the feedback speed is higher than or equal to 5 revolutions per minute.

7. The method for increasing the output current of a power switching device according to claim 1, wherein In Step 6, the adjustment formula for the control parameters is specifically: kp2 = (k2 / k1) × kp1, ki2 = (k1 / k2) × ki1; where kp1 is the low-frequency proportional control parameter of the current loop, kp2 is the high-frequency proportional control parameter of the current loop, k1 is the switching frequency in the low-frequency state, k2 is the switching frequency in the high-frequency state; ki1 is the low-frequency integral control parameter of the current loop, ki2 is the high-frequency integral control parameter of the current loop.

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