Load-Drive Controller Micro Step Current Control
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Solution Overview
Problem
Conventional load-drive controllers experience slow current decay and reduced follow-up capability during current decrease durations in micro step wave control, leading to prolonged time to reach setting current and increased vibration and noise in stepping motor drives.
Innovation Solution
A load-drive controller with a PWM control unit and a load current monitoring unit that compares the load current with a setting current, using a level shift circuit and peak hold circuit to determine the peak hold value, allowing for rapid control of load current increase or decrease based on these comparisons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional current control method with enforcement conducting mode is used, then the comparator mistake is prevented, but the load current decay becomes slow and follow-up capability is reduced
Solution Approach 1:
The patent applies dynamics by making the conducting mode switchable between two states: enforcement conducting mode (for reliability) and ordinary conducting mode (for speed). The control circuit dynamically selects the appropriate mode based on the operating phase, allowing the system to adapt between reliability and speed requirements at different times during the control cycle.
Solution Approach 2:
The patent changes the control parameter by switching between different conducting modes with different characteristics. In enforcement conducting mode, the control prioritizes reliability by preventing comparator mistakes. In ordinary conducting mode, the control prioritizes speed by allowing faster current decay. This parameter change enables the system to optimize performance based on real-time needs.
2Reliability
If enforcement conducting mode is applied continuously, then comparator reliability is improved, but the time to reach setting current is prolonged
Solution Approach 1:
The patent applies periodic action by alternating between enforcement conducting mode and ordinary conducting mode in a controlled sequence. The enforcement conducting mode is applied selectively during phases where reliability is critical (when comparator operation is needed), while ordinary conducting mode is applied during phases where speed is more important. This periodic switching optimizes both reliability and time efficiency.
Solution Approach 2:
The control circuit dynamically transitions between different conducting modes based on the operational requirements at each moment. Rather than using a static mode throughout, the system adapts its conducting mode to match the immediate needs of the control process, switching from enforcement mode to ordinary mode when reliability concerns are resolved.
3Speed
If ordinary conducting mode is used without enforcement mode, then current response is fast, but comparator inversion occurs causing mode transition errors
Solution Approach 1:
The patent applies preliminary anti-action by using enforcement conducting mode in advance during phases where comparator operation is expected. This preliminary measure prevents the comparator inversion problem before it can occur, ensuring reliable mode transitions. After this protective phase, the system switches to ordinary conducting mode to achieve faster current response without the risk of comparator errors.
Data Source
AI summary
In a load-drive controller, a first comparing unit compares a load current supplied from an H bridge circuit and a desired setting current; a PWM control unit generates a control signal to control the load current; a gate driver drives and controls output transistors of the H bridge circuit based on the control signal, and a load current monitoring unit determines which is larger a level shift equivalent value of the setting current or a peak hold equivalent value of the load current, and the PWM control unit controls increase or decrease of the load current based on a comparison result of the first comparing unit and on a determination result of the load current monitoring unit, so that the load current quickly reaches the setting current of a micro step drive during decrease of the setting current.