Brushless Motor Control Circuit Using Dynamic Commutation Contacts
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Solution Overview
Problem
Conventional circuit arrangements for brushless electric motors restrict the degrees of freedom in controlling the motor, particularly when using a single PWM contact, as the HIGHSIDE and LOWSIDE switching elements cannot be independently controlled, limiting the ability to drive individual winding phases and causing uneven power losses.
Innovation Solution
Configuring at least one commutation contact to be alternately controllable as both an input and an output, allowing it to be electrically connected to a PWM contact, enabling the generation of control signals with three possible digital states, thereby increasing control possibilities without requiring additional PWM contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single PWM contact is used to control multiple commutation signals through logic components, then the cost of the control component is reduced, but the degrees of freedom for controlling individual winding phases are restricted
Solution Approach 1:
The commutation contact is configured to be alternately controllable as input and output, making the control circuit dynamic rather than static. This allows the same physical contact to serve different functional roles depending on the operational phase, enabling independent control of HIGHSIDE and LOWSIDE switching elements without requiring additional PWM contacts
Solution Approach 2:
The commutation contact performs multiple functions by being alternately configured as input or output. It can tap off PWM signals when configured as input and drive switching elements when configured as output, allowing a single contact to replace what would traditionally require separate dedicated contacts for each function
2Device complexity
If HIGHSIDE and LOWSIDE switching elements are controlled by a single PWM signal, then the circuit complexity is reduced, but independent control of switching elements is not possible leading to uneven power losses
Solution Approach 1:
The circuit dynamically switches the role of the commutation contact between input and output states based on operational requirements. During phases requiring independent control of HIGHSIDE and LOWSIDE elements, the contact is configured as output to provide separate control signals, thereby reducing power losses without permanently increasing circuit complexity
Solution Approach 2:
The control method changes the operational parameters of the commutation contact by alternating its configuration between input and output modes. This parameter change enables the system to adapt the control strategy for switching elements based on the specific operational phase, optimizing power loss distribution
3Ease of operation
If logic components are used to combine PWM and commutation signals, then the control of motor terminals is achieved, but the control possibilities are restricted when commutation phases overlap
Solution Approach 1:
Instead of using fixed logic components that always perform the same logical operation, the invention dynamically reconfigures the commutation contact between input and output modes. This dynamic reconfiguration allows the system to handle overlapping commutation phases by providing independent control signals that logic components alone cannot generate
Data Source
AI summary
The invention specifies a circuit arrangement (1, 20) for controlling a brushless electric motor (37) with a control chip (2), particularly a microcontroller, which has a number of PWM contacts (8), which can be used to output a PWM signal, and a number of commutation contacts (5,5′, 6,6′, 7,7′), which can be used to output a commutation signal. In this case, provision is made for at least one commutation contact (5,5′, 6,6′, 7,7′) to be alternately controllable as an input and an output, for the at least one commutation contact (5,5′, 6,6′, 7,7′) to have its output electrically connected to a PWM contact (8), and for the commutation contact (5,5′, 6,6′, 7,7′) connected in this manner to be able to be contacted for the purpose of tapping off a control signal. Such a circuit arrangement (1,20) increases the control options for a given control chip (2). The number of PWM sources required is reduced.