Power Tool Motor Braking Control Without Bleeder Resistors
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Solution Overview
Problem
Existing power tools with permanent-magnet synchronous motors face issues of voltage spikes and reverse bus currents during braking, leading to potential device damage and power supply failure due to the need for additional bleeder resistors and control circuits, which increase cost and space.
Innovation Solution
A power tool with a control circuit that includes a driver circuit, controller, and parameter detection module, utilizing field-oriented control (FOC) to adjust input parameters and control the motor's braking, consuming braking current within the motor windings without additional elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional braking method with bleeder resistors is used, then voltage spikes and reverse bus current are suppressed, but device complexity and cost increase due to additional components
Solution Approach 1:
The patent extracts and eliminates the bleeder resistors from the braking circuit by implementing regenerative braking that feeds energy back to the power supply, thereby removing the need for additional protective components while maintaining reliability
Solution Approach 2:
The motor itself serves the dual function of both drive and braking through regenerative braking, where the motor acts as a generator during braking to convert kinetic energy back into electrical energy that is fed back to the power supply, making the system self-sufficient without external bleeder resistors
2Device complexity
If regenerative braking is implemented without additional components, then device complexity is reduced, but control precision must be maintained to prevent voltage spikes
Solution Approach 1:
The control circuit continuously monitors braking parameters and adjusts the regenerative braking process in real-time, using feedback signals to maintain precise control over the energy recovery process and prevent voltage spikes without requiring additional protective components
Solution Approach 2:
The braking control is made dynamic and adaptive, adjusting braking torque and energy recovery rate based on real-time system conditions, allowing the system to maintain precise control while using fewer components through intelligent, real-time parameter adjustment
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables safe and fast braking without additional electronic components, preventing voltage spikes and reverse currents, thus protecting the device and power supply.
Implementation Method 1
When a tool with a permanent-magnet synchronous motor brakes, the motor generally generates a relatively large voltage spike or a reverse bus current
Data Source
AI summary
A power tool includes: a motor including a rotor and multiple phases of stator windings; and a control circuit configured to control the working state of the motor. The control circuit includes: a driver circuit including multiple switching elements; a controller electrically connected to at least the driver circuit and capable of outputting a control signal to change the conducting states of the multiple switching elements in the driver circuit; and a parameter detection module configured to detect a working parameter of the motor. In response to a braking signal, the controller sets an input parameter of the control circuit according to a preset parameter and the working parameter to control output power of the motor and/or output torque of the motor, thereby controlling the motor to brake.