Interface Circuit for Single PWM BLDC Motor Control
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Solution Overview
Problem
The high cost of microcontrollers with multi-channel PWM capability is a significant expense in motor-control circuits, often requiring more sophisticated features than needed for controlling brushless DC motors, necessitating the development of a cost-effective solution.
Innovation Solution
An interface circuit that generates motor-phase control signals using a single PWM channel from a microcontroller, eliminating the need for multi-channel PWM capability, and can be implemented as a standalone IC or integrated into a pre-driver circuit, utilizing a binary selection signal to map PWM output signals to appropriate output terminals for motor-phase control states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a microcontroller with multi-channel PWM capability is used to control BLDC motor phases, then the motor control functionality is complete and reliable, but the cost of the microcontroller increases significantly
Solution Approach 1:
The patent divides the motor control function into two separate components: a simple microcontroller that generates only one PWM signal, and a dedicated interface circuit that receives this single PWM signal along with rotor position signals to generate all six motor phase control signals. This segmentation allows each component to be optimized independently - the microcontroller remains simple and low-cost, while the interface circuit handles the complexity of multi-phase control signal generation.
Solution Approach 2:
The interface circuit acts as an intermediary component between the simple microcontroller and the motor drive circuitry. It receives the single PWM output from the microcontroller and the rotor position information, then generates the complete set of six motor phase control signals. This intermediary absorbs the complexity of multi-channel PWM generation, allowing the use of a simpler, less expensive microcontroller.
2Device complexity
If a simple microcontroller with single PWM channel is used, then the cost is reduced, but the ability to directly control multiple motor phases is insufficient
Solution Approach 1:
The interface circuit is designed to perform multiple functions: it receives rotor position signals, generates complementary PWM signals for six different motor phases, and coordinates the timing of all phase control signals based on a single input PWM signal. This multi-functional interface circuit enables a simple microcontroller to control a three-phase BLDC motor effectively, as the interface circuit handles all the complexity of multi-phase control signal generation.
3Adaptability or versatility
If multi-channel PWM modules are included in microcontrollers, then motor control capability is enhanced, but the overall circuit cost increases
Solution Approach 1:
The patent extracts the multi-channel PWM generation functionality from the microcontroller and places it in a separate interface circuit. The microcontroller is left with only simple timing and single PWM generation capabilities, while the interface circuit contains the logic for generating all six motor phase control signals. This extraction allows the microcontroller to be much simpler and less expensive, while the interface circuit handles the enhanced adaptability and multi-phase control capability.
Data Source
AI summary
In one aspect of the teachings herein, an interface circuit obviates the need for a microcontroller with multi-channel PWM capability in the context of controlling a brushless, three-phase DC motor. Instead, the interface circuit generates the requisite set of motor-phase control signals using a single PWM channel from the microcontroller. The interface circuit is implemented as a standalone integrated circuit (IC) in one embodiment, and is integrated into a pre-driver circuit in another embodiment.