Motor Control Device Adjusting Pulse On-Time for Current Consistency
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Solution Overview
Problem
Existing motor control devices for brushless motors experience significant variations in three-phase drive currents due to individual differences in switching elements, leading to deviations in magnetic flux and magnetic noise generation.
Innovation Solution
A motor control device with a bridge circuit and control circuit that adjusts the on-time length of control pulses to switching elements, using a set value changing unit to correct variations in drive currents, ensuring consistent magnetic flux across phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If PWM control is applied to switching elements with individual performance differences, then motor control functionality is achieved, but significant variation in three-phase drive currents occurs
Solution Approach 1:
The patent applies parameter changes by adjusting the on-time length of control pulses for each switching element based on its individual characteristics. The control circuit measures the actual on-time of each switching element and modifies the control pulse parameters (on-time length) to compensate for individual differences, thereby achieving consistent three-phase drive currents despite variations in switching element performance
Solution Approach 2:
The patent implements feedback control by measuring the actual on-time of each switching element and using this information to adjust the control pulse parameters. The control circuit continuously monitors the switching element performance and modifies the control signals accordingly, creating a closed-loop system that eliminates current variations caused by individual element differences
2Device complexity
If individual differences in switching elements are not compensated, then device complexity is reduced, but magnetic flux deviation and magnetic noise occur
Solution Approach 1:
The patent applies self-service by having the control circuit automatically measure and adjust control pulse parameters for each switching element without requiring external calibration or manual intervention. The system self-calibrates by detecting individual switching element characteristics and autonomously modifies control signals to eliminate current variations, preventing magnetic noise generation
Data Source
AI summary
A motor control device generates three-phase drive currents having a phase difference by combining on-off actions of switching elements and supplies the three-phase drive currents to three-phase coils of a brushless motor. The motor control device includes a drive circuit including a bridge circuit that uses multiple switching elements and a control circuit that sets a control pulse, which causes each of the switching elements to perform on-off actions. The control circuit includes a control pulse generating unit that generates a control pulse. The control circuit further includes a set value retaining unit that retains a set value of an on-time length of the control pulse, which is referred to when the control pulse is generated in the control pulse generating unit. The control circuit further includes a set value changing unit that changes the set value retained in the set value retaining unit.