PWM Semiconductor Device for Motor Drive Rotor Position Estimation
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Solution Overview
Problem
Conventional three-phase motor drive devices face challenges in accurately estimating the position of a rotor due to the complexity of software processing, which makes it difficult to complete processes within one carrier signal cycle without increasing CPU processing speed, leading to increased costs.
Innovation Solution
A semiconductor device that generates N-phase pulse width modulation signals for an inverter circuit, utilizing a first register, correction buffer, counters, selectors, comparison units, and a pulse width modulation control unit to adjust the active period of PWM signals, allowing for secure AD conversion time without changing the on-duty of the signal, thus enabling improved rotor position estimation without increasing CPU speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If software processing is made more complex to improve rotor position estimation accuracy, then measurement precision is improved, but device complexity increases and processing time exceeds one carrier signal cycle
Solution Approach 1:
The patent divides the PWM control system into multiple independent hardware counters (first counter for timing, second counter for PWM generation) that operate in parallel. This segmentation allows the system to perform complex timing operations and rotor position calculations simultaneously without software interference, resolving the contradiction between measurement precision and device complexity by distributing functions across dedicated hardware components rather than relying on complex software processing.
Solution Approach 2:
The patent introduces a correction buffer as an intermediary component between the first counter and the second counter. This buffer stores correction values that adjust PWM signal timing without requiring complex software calculations during operation. The intermediary buffer simplifies the overall system architecture by pre-calculating and storing timing corrections, thereby improving rotor position estimation accuracy while avoiding increased software processing complexity.
2Productivity
If CPU processing speed is increased to complete all processes within one carrier signal cycle, then productivity is improved, but device cost increases
Solution Approach 1:
The patent replaces the mechanical/software-based timing control system with a dedicated hardware counter system. The first counter and second counter are hardware components that automatically generate and synchronize PWM signals without requiring CPU intervention for timing operations. This substitution eliminates the need for high-speed CPU processing to complete timing operations within one carrier signal cycle, thereby improving productivity without increasing device cost through higher CPU speed requirements.
Solution Approach 2:
The hardware counter system operates autonomously to manage PWM timing and synchronization without requiring continuous CPU control. The first counter self-generates timing signals, and the second counter automatically adjusts PWM generation based on correction values from the buffer. This self-service capability allows the system to complete all timing processes within one carrier signal cycle using standard-speed CPUs, improving productivity while avoiding the cost increase associated with high-speed processors.
3Measurement precision
If AD conversion time is secured by adjusting PWM signal timing, then measurement precision is improved, but the on-duty of the signal changes
Solution Approach 1:
The patent performs preliminary timing correction by storing correction values in the correction buffer before PWM signal generation. These pre-calculated correction values adjust the timing of the second counter to secure adequate AD conversion time without requiring real-time modifications to PWM signal duty cycles. By performing the timing adjustment in advance through hardware, the system achieves precise AD conversion timing while maintaining the original PWM signal on-duty, resolving the contradiction between measurement precision and signal duration.
Data Source
AI summary
The semiconductor device according to the present invention generates pulse width modulation signals for controlling inverter circuits that drive a motor. The semiconductor device includes: a first register which holds values for determining a period in which each pulse width modulation signal becomes active; a correction buffer which holds a correction value; a first counter; a second counter which counts a value obtained by temporally advancing or delaying a count value of the first counter; a selector which selects the count value of the first counter or the count value of the second counter; and a pulse width modulation control unit which generates each pulse width modulation signal, logical values of which are switched in a timing when the selected count value matches the value held by the first register.