A h-bridge adaptive attenuation control system applied to motor driving

Abstract

This invention relates to the field of motor drive technology, specifically to an H-bridge adaptive attenuation control system for motor drives. This system can adaptively adjust the ratio of fast / slow attenuation in real time according to external factors, thereby ensuring that the H-bridge maintains good performance under various operating conditions and improving the performance of the motor driven by the H-bridge circuit. The system includes an H-bridge, a digital control module, an analog comparator, and a digital-to-analog converter (DAC). The control signal output terminal of the digital control module is connected to the input terminal of the H-bridge, and the digital signal output terminal is connected to the input terminal of the DAC. The output terminal of the DAC is connected to one input terminal of the analog comparator, and the output terminal of the H-bridge is connected to the other input terminal of the analog comparator and a tail current sensing resistor. The analog comparator compares the tail current magnitude with a preset current value of the digital control module and sends the comparison result to the digital control module. The H-bridge adjusts its attenuation mode by flipping the comparison signal given by the digital control module.

Description

Technical Field

[0001] This invention relates to the field of motor drive technology, specifically to an H-bridge adaptive attenuation control system applied to motor drives. Background Technology

[0002] In the H-bridge drive circuit, such as Figure 1 As shown, four MOSFETs (101-104) form an H-bridge to drive the motor coil. When the H-bridge is working, if MOSFETs 101 and 104 are simultaneously turned on, the current direction is as shown by the solid arrow 107 in the figure. Since the motor load is a winding coil, it exhibits inductive characteristics. When the H-bridge reaches the required current, it will turn off MOSFETs 101 and 104, but due to the inductive characteristics, the current will continue to flow in its original direction (freewheeling characteristic). There are two freewheeling modes at this time:

[0003] The first method involves turning off the upper MOSFETs 101 and 103, and turning on the lower MOSFETs 102 and 104. The current direction in this case is shown by the dashed arrow 106. Due to its operating characteristics, this freewheeling method results in a smaller current, so the voltage difference across the load decreases more slowly, a phenomenon known as slow decay.

[0004] The second method involves shutting down the previously operating MOSFETs 101 and 104, and turning on the reverse-biased MOSFETs 102 and 103. The current direction in this case is shown by the dashed arrow 105. This freewheeling method generates a larger current, resulting in a faster voltage drop across the load, a phenomenon known as fast decay.

[0005] The relationship between current and fast / slow decay described above is as follows: Figure 2 As shown, 200 is one of the PWM cycles of the H-bridge driving the load. Cycle 201 is the time period when the H-bridge outputs current to the load. During this period, MOSFETs 101 and 104 are turned on, and the current shows an upward trend. When the current reaches the target value, MOSFETs 101 and 104 are turned off, and the H-bridge enters the decay phases 202 and 203. Phase 202 is the fast decay phase mentioned above, and it can be seen from the figure that the current decreases faster than in phase 203 (slow decay). If all cycles outside of power supply cycle 201 are fast decay cycles 202, it is called fast decay mode; if all cycles outside of power supply cycle 201 are slow decay cycles 203, it is called slow decay mode; of course, there are also... Figure 2 The diagram shows a combination of fast and slow decay, a condition known as a mixed decay mode.

[0006] Fast and slow decay each have their advantages. Fast decay allows the current to decay quickly, avoiding waveform distortion caused by rapid changes in the current waveform. However, this rapid change results in larger current fluctuations, which is detrimental to the smooth operation of the motor. Slow decay, on the other hand, is prone to distortion when the current waveform changes rapidly, but the slow change produces a smoother current waveform and motor operating state. Generally speaking, hybrid decay combines the advantages of both fast and slow decay, greatly improving the performance of H-bridge decay. However, the operating conditions of H-bridge drive motors vary greatly: speed changes, output torque changes, etc. This means that a fixed-ratio hybrid decay mode cannot meet the high-performance requirements under all operating conditions. Summary of the Invention

[0007] To address the issue that existing H-bridges cannot adaptively adjust the fast / slow attenuation ratio of the H-bridge drive signal in real time based on the operating state and external device environment, thus affecting the motor performance driven by the H-bridge circuit, this new technology can adaptively adjust the fast / slow attenuation ratio in real time according to external factors. This ensures that the H-bridge maintains good performance under various operating conditions, thereby improving the motor performance driven by the H-bridge circuit.

[0008] The technical solution is as follows: An H-bridge adaptive attenuation control system for motor drive includes an H-bridge, characterized in that it further includes a digital control module, an analog comparator, and a digital-to-analog converter. The control signal output terminal of the digital control module is connected to the input terminal of the H-bridge, and the digital signal output terminal is connected to the input terminal of the digital-to-analog converter. The output terminal of the digital-to-analog converter is connected to one input terminal of the analog comparator, and the output terminal of the H-bridge is connected to the other input terminal of the analog comparator and a tail current sensing resistor. The analog comparator compares the tail current magnitude with a preset current value of the digital control module and sends the comparison result to the digital control module. The H-bridge adjusts its attenuation mode by flipping according to the comparison signal given by the digital control module.

[0009] Its further feature is that, in the working cycle of a PWM drive waveform, when the tail current is between the current target value and the current tolerance value, the H-bridge adopts a fast decay mode, and when the tail current is less than the current tolerance value, the H-bridge adopts a slow decay mode.

[0010] When the tail current fails to reach the preset current value within the current target value acquisition period, the digital control module adjusts the current tolerance value to realize the ratio of the fast and slow decay modes of the H-bridge.

[0011] In a work cycle containing at least two PWM drive waveforms, a period during which the digital control module does not respond to the output of the analog comparator after the MOSFET is started is designated as a prohibition period. When the decay of the previous work cycle is insufficient, the tail current exceeds the current target value during the prohibition period. In this case, the digital control module reduces the current tolerance value and increases the difference between the current tolerance value and the current target value, increasing the fast decay ratio and shifting the fast decay reversal point backward until it falls within the current target value acquisition period. When the decay of the previous work cycle is excessive or the current waveform changes significantly, the tail current does not reach the current target value by the end of the current target value acquisition period. In this case, the digital control module increases the current tolerance value and decreases the difference between the current tolerance value and the current target value, increasing the slow decay ratio and shifting the fast decay reversal point forward until it falls within the current target value acquisition period. When the decay of the previous work cycle is normal, the tail current reaches the current target value during the current target value acquisition period. If the time of reaching the target value does not fall at the preset optimal target point, the digital control module increases or decreases the current tolerance value to adjust the ratio of fast and slow decay. The fast decay reversal point gradually approaches the optimal target point until it reaches the control error range.

[0012] By employing this invention, the digital control module processes the comparison between the tail current magnitude and the preset current value, and then controls the H-bridge to flip to adjust the attenuation mode. This achieves real-time adaptive adjustment of the fast / slow attenuation ratio based on external factors, thereby ensuring that the H-bridge maintains good performance under various operating conditions and improving the performance of the motor driven by the H-bridge circuit. Attached Figure Description

[0013] Figure 1 Here is the schematic diagram of an existing H-bridge driver circuit;

[0014] Figure 2 This is a graph showing the attenuation mode of an existing H-bridge drive circuit.

[0015] Figure 3 This is a schematic diagram of the control system of the present invention;

[0016] Figure 4 This is a curve showing the attenuation state of the H-bridge in this invention.

[0017] Figure 5 Add an internal operating logic diagram to the digital control module. Detailed Implementation

[0018] See Figures 3 to 5As shown, an H-bridge adaptive attenuation control system for motor drive includes an H-bridge, a digital control module 300, an analog comparator 301, and a digital-to-analog converter 302. The H-bridge is composed of MOSFETs 101, 102, 103, and 104, and a load motor. The control signal output terminal of the digital control module 300 is connected to the input terminal of the H-bridge, and the digital signal output terminal is connected to the input terminal of the digital-to-analog converter 302. The output terminal of the digital-to-analog converter 302 is connected to one input terminal of the analog comparator 301, and the output terminal of the H-bridge is connected to the other input terminal of the analog comparator 301 and the tail current sensing resistor 311. The analog comparator 301 compares the tail current magnitude with the preset current value of the digital control module 300 and sends the comparison result to the digital control module 300. The H-bridge will adjust the attenuation mode according to the comparison signal given by the digital control module 300. The digital signal provided by the digital control module 300 to the digital-to-analog converter 302 varies depending on its internal state, thereby enabling the analog comparator 301 to compare multiple level values. It mainly judges and adjusts the H-bridge attenuation working state based on the state of the tail current of the H-bridge. In this embodiment, the tail current sensing resistor 311 is provided, which may include auxiliary filtering devices. For simplicity, it is not shown and does not affect the description of the principle of the present invention.

[0019] according to Figure 4 The target current value 409 and the tolerance current value 410 are digital values ​​sent by the digital control module 300 to the digital-to-analog converter 302 according to the working status. The H-bridge will adjust its decay mode according to the comparison signal given by the analog comparator 301. In the working cycle of a PWM drive waveform, when the tail current is between the target current value and the tolerance current value, the H-bridge adopts the fast decay mode. When the tail current is less than the tolerance current value, the H-bridge adopts the slow decay mode.

[0020] When the tail current fails to reach the preset current value within the current target value acquisition period, the digital control module 300 adjusts the current tolerance value to achieve the ratio of the H-bridge fast and slow decay modes. This is explained in detail below: According to... Figure 4Period 400 is the working cycle of one PWM drive waveform of the H-bridge, and the other periods are similar. Period 402 is the disable period. Because the tail current of the H-bridge is prone to generating pulses during MOS switching, to avoid the adverse effects of these pulses on the control system, there will be a short disable period after the MOS transistors 101 and 104 of the H-bridge are turned on. During this period, the digital control module 300 does not respond to the output of the analog comparator. Period 401 is the current target value acquisition period. The digital control module 300 presets that the tail current of the H-bridge should reach the preset current value within this period, that is, the comparison signal of the analog comparator 302 will flip within this period. If not, the digital control module 300 will adjust the current tolerance value 410, that is, change the difference 407 between the current tolerance value 410 and the current target value 409. Since the adjustment of the difference 407 by the digital control module 300 is equivalent to adjusting the ratio of fast / slow decay of the H-bridge, ... Figure 4 It can be seen that this ratio can be adjusted between 0% and 100%. This adjustment will cause the comparison result flip points 411 and 412 of the analog comparator 302 to move horizontally on the time axis. Flip point 411 is the fast decay flip point and 412 is the slow decay flip point.

[0021] In a work cycle containing at least two PWM drive waveforms, if the decay of the previous work cycle is insufficient and the tail current exceeds the current target value during the prohibition period 402, the digital control module 300 reduces the current tolerance value 410 and increases the difference between the current tolerance value 410 and the current target value 409, thereby increasing the fast decay ratio and shifting the fast decay inversion point 411 backward (i.e., to the right on the time axis) until it falls within the current target value acquisition period 401. If the decay of the previous work cycle is too large or the current waveform changes significantly, and the tail current does not reach the current target value 409 by the end of the current target value acquisition period 401, the digital control module 300 increases the current tolerance value 410 and decreases the current tolerance value 409. The difference between 410 and the current target value 409 increases the slow decay ratio, and the fast decay reversal point 411 moves forward until it falls within the current target value acquisition period 401. When the decay of the previous working cycle is normal, the tail current reaches the current target value 109 in the current target value acquisition period 401. If the time of reaching the target value does not fall on the preset optimal target point 408, the digital control module 300 increases or decreases the current tolerance value 410 to adjust the ratio of fast and slow decay. The fast decay reversal point 411 gradually approaches the optimal target point 408 until it reaches the control error range. Since the magnitude of this adjustment is small, the digital control module 300 will use a small adjustment step in this process to achieve the effect of fine adjustment.

[0022] The internal operating logic of the digital control module 300 is as follows: Figure 5As shown, there are essentially two detection / adjustment loops. Each judgment / adjustment uses one PWM cycle; then the entire judgment process is repeated in the next cycle. In the first cycle, the system uses pre-set initial values, including: current target value 409, current tolerance value 410, prohibition period 402, current target value acquisition period 401, and the position of the optimal target point 408. The current target value 409 is adjusted according to the current value given by the motor control system, and the remaining values ​​are iteratively adjusted according to the value of the previous cycle. Through the above mechanism, it can be ensured that the adaptive attenuation control system of the present invention can adjust in real time according to the characteristics of the H-bridge environment and working state, maximizing the H-bridge to adopt the optimal attenuation mode to achieve optimal working performance.

Claims

1. An H-bridge adaptive attenuation control system for motor drives, comprising an H-bridge, characterized in that, It also includes a digital control module, an analog comparator, and a digital-to-analog converter. The control signal output of the digital control module is connected to the input of the H-bridge, and the digital signal output is connected to the input of the digital-to-analog converter. The output of the digital-to-analog converter is connected to one input of the analog comparator. The output of the H-bridge is connected to the other input of the analog comparator and a tail current sensing resistor. The analog comparator compares the tail current magnitude with a preset current value of the digital control module and sends the comparison result to the digital control module. The H-bridge adjusts its attenuation mode by flipping according to the comparison signal given by the digital control module. During the working cycle of a PWM drive waveform, when the tail current is between the target current value and the current tolerance value, the H-bridge... The bridge adopts a fast decay mode. When the tail current is less than the current tolerance value, the H-bridge adopts a slow decay mode. When the tail current does not reach the current preset value within the current target value acquisition period, the digital control module adjusts the current tolerance value to realize the ratio of the fast and slow decay modes of the H-bridge. In a working cycle containing at least two PWM drive waveforms, a period in which the digital control module does not respond to the output result of the analog comparator after the MOSFET is started is defined as the prohibition period. When the decay of the previous working cycle is insufficient, the tail current is greater than the current target value within the prohibition period. Then, the digital control module reduces the current tolerance value and increases the difference between the current tolerance value and the current target value. The fast decay ratio increases, and the fast decay flip point moves backward until it falls within the current target value acquisition period. When the decay of the previous working cycle is too large or the current waveform changes significantly, and the tail current does not reach the current target value by the end of the current target value acquisition period, the digital control module increases the current tolerance value and reduces the difference between the current tolerance value and the current target value. The slow decay ratio increases, and the fast decay reversal point moves forward until it falls into the current target value acquisition period. When the decay of the previous working cycle is normal, the tail current reaches the current target value during the current target value acquisition period. If the time of reaching the target value does not fall on the preset optimal target point, the digital control module increases or decreases the current tolerance value to adjust the ratio of fast and slow decay. The fast decay reversal point gradually approaches the optimal target point until it reaches the control error range.

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