Method for improving output current of power switch device

Abstract

The invention belongs to the technical field of industrial control, relates to a motor motion control application scene, and particularly provides a method for improving the output current of a power switching device, which is used for improving the current output capability of the power switching device and realizing the maximization of working potential, so that the system cost and the system heat dissipation design requirement are reduced. The working characteristics of a power switch device are researched in detail, the feedback rotating speed of a motor encoder is creatively put forward to serve as a representation value, switching judgment conditions for the switching frequency are further put forward on the basis of the representation value, the switching judgment conditions comprise the frequency reduction condition and the frequency increase condition, and in the motor motion control process, the frequency of the motor is controlled. The high and low frequency switching of the switching frequency is automatically completed, the current output capability of the power switching device is effectively improved on the premise of ensuring the motor control performance, the working potential of the power switching device is maximized, and the reduction of the system cost and the system heat dissipation design requirement are facilitated.

Description

Technical Field

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

[0002] Power switching devices are widely used in power supply, wind power, solar energy, electric vehicles, and industrial automation. As core devices in these fields, if the capacity of the power switching device is too large, it will cause waste and fail to maximize the efficiency of the device. Moreover, devices with larger capacity will bring higher system costs. If the capacity of the power switching device is too small, the device will work under high current conditions, the junction temperature will increase, which may bring system risks and even cause the power switching device to explode and the system to fail. Therefore, how to optimize the use of power switching devices becomes 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 switching device, so as to improve the current output capacity of the power switching device and maximize the working potential, thereby reducing the system cost and the system heat dissipation design requirements; the present invention conducts a detailed study on the working characteristics of the power switching device, and 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 the characterization value, including frequency reduction conditions and frequency increase conditions. During the motor motion control process, the high and low frequency switching of the switching frequency is automatically completed. Under the premise of ensuring the motor control performance, the current output capacity of the power switching device is effectively improved, the working potential of the power switching device is maximized, and it is beneficial to reduce the system cost and the system heat dissipation design requirements.

[0004] To achieve the above object, the technical solution adopted by the present invention is: A method for increasing the output current of a power switch device comprises the following steps: Step 1. Initialize the system and initialize the switching frequency of the power switch device in the PWM peripheral module of the MCU to a high frequency state; Step 2. The control platform enters the enabled control state, receives the speed command or position command, and the PWM peripheral module sends a PWM signal to perform speed control or position control on the motor; Step 3. Detect the feedback speed of the motor encoder in real time and determine whether the feedback speed reaches the frequency reduction condition. If the frequency reduction condition is reached, execute step 4; otherwise, maintain the current state to control the motor; Step 4. The control platform maintains the enabled control state, and the MCU configures the PWM peripheral module to switch the switching frequency of the power switch device to a low-frequency state; at the same time, the control platform matches the control parameters according to the switching frequency; Step 5. Detect the feedback speed of the motor encoder in real time and determine whether the feedback speed reaches the frequency increase condition. If the frequency increase condition is reached, execute step 6; otherwise, maintain the current state to control the motor; Step 6. The control platform maintains the enabled control state, and the MCU configures the PWM peripheral module to switch the switching frequency of the power switch device to a high-frequency state; at the same time, the control platform matches the control parameters according to the switching frequency; Step 7. The control platform continues to control the motor in the enabled control state until receiving the next enable command and ending the working state.

[0005] Furthermore, in step 1, the high frequency state is specifically 12 kHz.

[0006] Furthermore, in step 3, the frequency reduction condition is specifically: the feedback speed is lower than 5 rpm and the duration is greater than 3 seconds.

[0007] Furthermore, in step 4, the low frequency state is specifically 6 kHz.

[0008] Furthermore, in step 4, the adjustment formula of the control parameter is specifically: kp1=(k1 / k2)×kp2, ki1=(k1 / k2)×ki2; 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 low-frequency state switching frequency, k2 is the high-frequency state switching frequency; ki1 is the current loop low-frequency integral control parameter, ki2 is the current loop high-frequency integral control parameter.

[0009] Furthermore, in step 6, the frequency increase condition is specifically: the feedback speed is greater than or equal to 5 rpm.

[0010] Furthermore, in step 6, the adjustment formula of the control parameter is specifically: kp2=(k2 / k1)×kp1, ki2=(k1 / k2)×ki1; 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 low-frequency state switching frequency, k2 is the high-frequency state switching frequency; ki1 is the current loop low-frequency integral control parameter, ki2 is the current loop high-frequency integral control parameter.

[0011] Based on the above technical solution, the beneficial effects of the present invention are: The present invention provides a method for increasing the output current of a power switch device. Through a detailed study of the working characteristics of the power switch device, a creative proposal is made to use the feedback speed of a motor encoder as a characterization value. Based on the characterization value, a switching decision condition for the switching frequency is further proposed, including a frequency reduction condition and a frequency increase condition. In the motor motion control process, the PWM frequency (the working frequency of the switch device) is initialized to a high frequency (12kHz), and the servo driver executes a motor control process that is the same as a conventional control process; and the feedback speed of the motor encoder is monitored in real time. When the set frequency reduction condition is met, that is, the feedback speed is lower than 5RPM and the duration is greater than 3 seconds, the PWM peripheral module configuration is modified to switch the PWM frequency to a low frequency. The frequency (6kHz) is changed, and the current loop control parameters are modified to make the motor enter low-frequency control, which effectively reduces the shell temperature of the power device, thereby improving the current output capacity of the power switch device and adapting to a larger load; at the same time, when the feedback speed is higher than 5RPM, the predetermined frequency increase condition is reached, and the PWM peripheral configuration is modified again to switch the PWM frequency to high frequency (12kHz), 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, and the current output capacity of the power switch device is effectively improved while ensuring the motor control performance, so that the working potential of the power switch device is maximized, which is conducive to reducing system costs and system heat dissipation design requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is the PWM waveform output by the MCU when the switching frequency of the power switching device switches from high frequency to low frequency.

[0013] Figure 2 This is the PWM waveform output by the MCU when the switching frequency of the power switching device switches from low frequency to high frequency.

[0014] Figure 3 A schematic flow chart of a method for increasing the output current of a power switch device provided by the present invention. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solution and beneficial effects of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0016] The present invention provides a method for increasing the output current of a power switch device. In terms of working principle, the data sheet of the power switch device will give the nominal current, and the nominal current is the instantaneous current, not the rated current of the power switch device. Since the rated current of the power switch device depends on the heat dissipation of the system and is related to the system design, the better the heat dissipation of the system, the higher the rated current of the power switch device. Therefore, the rated current of the power switch device is not given in the data sheet. However, it can be seen from the data sheet of the power switch device that the rated current of the device is related to the shell temperature. The rated current is defined at a given shell temperature. The lower the shell temperature, the greater the output current of the power switch device. The specific relationship is expressed as: T vimax =T c + R thjc ×(I cn ×V ce_sat ), T vimax The maximum allowable junction temperature of the power switch device, usually a fixed value, T vimax =175℃; T c is the case temperature of the power switch device, R thjc is the junction-to-case resistance of the power switching device, I cn is the collector rated current of the power switching device; V ce_sat is the collector-emitter saturation voltage of the power switch device, which is usually a fixed value. c Can increase the collector rated current I cn The direct way to reduce the shell 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 under the premise of meeting the system control performance to achieve the goal of reducing the shell temperature T. c The purpose is to improve the current output capacity of the power switching device.

[0017] Through testing, such as Figure 1 The figure shows the PWM waveform output by the MCU when the switching frequency of the power switch device switches from high frequency to low frequency. Figure 2 The figure shows the PWM waveform output by the MCU when the switching frequency of the power switch device switches from low frequency to high frequency; it can be seen from the figure that the high and low frequency switching process switches smoothly, and there is no abnormal situation where both the upper bridge arm and the lower bridge arm are open. In motor motion control, a higher switching frequency means a higher control bandwidth, which means a faster response speed, and thus achieves higher control performance, but a higher switching frequency will also bring greater switching losses, thereby reducing the current output capacity of the power switch device.

[0018] 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 the characterization value, including frequency increase conditions and frequency reduction conditions; the switching frequency of the power switching device is initialized to a high-frequency state to achieve high-performance motor control, and the characterization value is monitored in real time. When the characterization value reaches the frequency reduction condition, the switching frequency of the power switching device is switched to a low-frequency state, and the control parameters are adjusted accordingly, thereby reducing switching losses and increasing the output current of the power switching device; on this basis, based on the method proposed in the present invention, the current output potential of the power switching device can be fully utilized, and the system cost and system heat dissipation design requirements can be reduced.

[0019] Based on the above working principle, the present invention provides a specific embodiment, the process of the method for increasing the output current of the power switch device is as follows: Figure 3 As shown, the specific steps include: 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 12kHz; at the same time, initialize the control parameters of the motor; and match and set the registers of the MCU to meet the requirements of motor control; the MCU is not limited to any type, it can be a DSP (Digital Signal Processor) digital processor or an ARM (Advanced RISCMachine) chip. Both DSP digital processors and ARM chips are commonly used MCUs for power switch devices; After the system initialization is completed, the control platform enters the ready state, waiting to receive commands from the host computer or main controller; Step 2. The control platform enters the enabled control state, receives the speed command or position command, and the PWM peripheral module sends a PWM signal to control the speed or position of the motor; the control platform usually receives the speed command or position command issued by the host computer or the main controller through bus communication; Step 3. Detect the feedback speed of the motor encoder in real time and determine whether the feedback speed reaches the frequency reduction condition. If the frequency reduction condition is reached, execute step 4; otherwise, maintain the current state to control the motor; The frequency reduction condition is specifically: the feedback speed is lower than 5 rpm and the duration is greater than 3 seconds. More specifically, the operating frequency of the power switch device is reduced only when the feedback speed is lower than 5 rpm and the duration of the feedback speed being lower than 5 rpm is greater than 3 seconds. The monitoring process of the encoder feedback speed is as follows: the MCU collects the encoder position in real time and calculates the motor speed based on the encoder position information; Step 4. The control platform maintains the enabled control state, and the MCU configures the PWM peripheral module to switch the switching frequency of the power switch device to a low-frequency state, specifically 6kHz; at the same time, the control platform matches the control parameters according to the switching frequency to adapt the control parameters to the low-frequency state; Since switching the switching frequency to a low frequency state will reduce the system bandwidth, it is necessary to match and adjust the corresponding current loop control parameters, otherwise it may cause control abnormality; the specific adjustment formula is: kp1=(k1 / k2)×kp2, ki1=(k1 / k2)×ki2; 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 low-frequency state switching frequency, k2 is the high-frequency state switching frequency; ki1 is the current loop low-frequency integral control parameter, ki2 is the current loop high-frequency integral control parameter; Step 5. Detect the feedback speed of the motor encoder in real time and determine whether the feedback speed reaches the frequency increase condition. If the frequency increase condition is reached, execute step 6; otherwise, maintain the current state to control the motor; The frequency-up condition is specifically: the feedback speed is higher than or equal to 5 rpm. More specifically, only when the feedback speed is higher than or equal to 5 rpm, the operating frequency of the power switch device is frequency-up processed; Step 6. The control platform maintains the enabled control state, and the MCU configures the PWM peripheral module to switch the switching frequency of the power switch device to a high-frequency state; at the same time, the control platform matches the control parameters according to the switching frequency to adapt the control parameters to the high-frequency state; the adjustment formula is as follows: kp2=(k2 / k1)×kp1, ki2=(k1 / k2)×ki1; 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 low-frequency state switching frequency, k2 is the high-frequency state switching frequency; ki1 is the current loop low-frequency integral control parameter, ki2 is the current loop high-frequency integral control parameter; Step 7. The control platform continues to control the motor in the enabled control state until receiving the next enabling command and terminating the working state; thus, this embodiment effectively improves the current output of the power switch device during the motor motion control process.

[0020] The above description is only a specific implementation mode of the present invention. Any feature disclosed in this specification, unless otherwise stated, can be replaced by other alternative features that are equivalent or have similar purposes; all the disclosed features, or all the steps in the methods or processes, 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: The following steps are involved: Step 1. Initialize the system and set the switching frequency of the power switch device in the PWM peripheral module of the MCU to a high frequency state. Step 2. The control platform enters the enabled control state, receives the speed command or position command, and the PWM peripheral module sends a PWM signal to perform speed control or position control on the motor; Step 3. Detect the feedback speed of the motor encoder in real time and determine whether the feedback speed reaches the frequency reduction condition. If the frequency reduction condition is reached, execute step 4; otherwise, maintain the current state to control the motor; Step 4. The control platform maintains the enabled control state, and the MCU configures the PWM peripheral module to switch the switching frequency of the power switch device to a low-frequency state; at the same time, the control platform matches the control parameters according to the switching frequency; Step 5. Detect the feedback speed of the motor encoder in real time and determine whether the feedback speed reaches the frequency increase condition. If the frequency increase condition is reached, execute step 6; otherwise, maintain the current state to control the motor; Step 6. The control platform maintains the enabled control state, and the MCU configures the PWM peripheral module to switch the switching frequency of the power switch device to a high-frequency state; at the same time, the control platform matches the control parameters according to the switching frequency; Step 7. The control platform continues to control the motor in the enabled control state until receiving the next enable command and ending the working state.

2. The method for increasing the output current of a power switch 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 switch device according to claim 1, characterized in that: In step 3, the frequency reduction condition is specifically: the feedback speed is lower than 5 rpm and the duration is greater than 3 seconds.

4. The method for increasing the output current of a power switch device according to claim 1, characterized in that: In step 4, the low frequency state is specifically 6 kHz.

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

6. The method for increasing the output current of a power switch device according to claim 1, characterized in that: In step 6, the frequency increase condition is specifically: the feedback speed is greater than or equal to 5 rpm.

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

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