Stationary Position Detection Circuit for Sensorless Motor Drive
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Solution Overview
Problem
Current Hall sensorless motor detection methods face challenges in accurately detecting rotor position without Hall sensors, particularly due to the need for large kickback currents that cause vibrations and limited information capture from short kickback periods.
Innovation Solution
A stationary position detection circuit using a current amount detector, time counter, time difference amplifier, and position determinator, which alternates current direction and amplifies electrical signals from time measurements to accurately determine rotor position without high kickback currents, reducing vibrations and improving detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large kickback current is supplied to generate a large kickback voltage for detecting the minuscule inductance difference, then the rotor position detection capability is improved, but vibrations are caused
Solution Approach 1:
The patent applies periodic action by repeatedly alternating the current direction multiple times (first direction and second direction) rather than using a single large kickback current pulse. This periodic measurement approach allows accumulation of detection data over multiple cycles, improving measurement precision while using smaller current amplitudes that do not cause harmful vibrations.
Solution Approach 2:
The patent implements continuity of useful action by continuously alternating the current between first and second directions for multiple periods, rather than using a discrete large kickback current. This continuous periodic measurement maintains detection capability while avoiding the harmful effects of large instantaneous currents.
2Speed
If the kickback time is measured for a very short period during kickback occurrence, then the detection speed is improved, but the information may not be sufficiently detected
Solution Approach 1:
The patent resolves this contradiction by performing multiple periodic measurements of the time period during which current flows in each direction. By accumulating data from multiple periods rather than relying on a single short measurement, the system achieves both sufficient information detection and maintains fast response capability.
Solution Approach 2:
The patent applies preliminary action by pre-determining the number of alternating periods to be executed and preparing the measurement framework in advance. This allows the system to efficiently collect sufficient information through multiple rapid measurements without sacrificing detection speed.
3Object-generated harmful factors
If the alternating current value is reduced to minimize vibrations, then the harmful vibrations are suppressed, but the detection accuracy may be insufficient
Solution Approach 1:
The patent resolves this contradiction by using periodic action to accumulate detection data from multiple measurement cycles. By performing repeated measurements with smaller alternating current values and accumulating the results, the system achieves both vibration suppression and sufficient detection accuracy through statistical accumulation of measurement data.
Solution Approach 2:
The patent applies partial action by using smaller alternating current values than the single large kickback current, performing multiple partial measurements instead of one excessive measurement. This approach reduces harmful vibrations while the cumulative effect of multiple measurements provides sufficient detection accuracy.
Data Source
AI summary
A stationary position detection circuit and a motor drive circuit capable of more properly detecting the rotor position are disclosed. The stationary position detection circuit supplies an alternating current to each phase load of the motor. The time during which the current flows in a first direction and the time during which the current flows in a second direction opposite to the first direction are converted into electrical signals and amplified. In accordance with the value of the electrical signals, the position of the motor rotor in stationary mode is determined. The use of the alternating current, unlike the kickback voltage, makes it possible to improve the detection accuracy by amplifying the electrical signals with an increased number of alternations. An increased number of alternations can amplify the electrical signals without increasing the value of the alternating current, and therefore, unlike in the case of the kickback voltage, the alternating current of a large value is not required. As a result, the alternating current can be reduced to a small value and the vibration can be suppressed.