BLDC Motor Boost Mode Back-EMF Power Recovery
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Solution Overview
Problem
In systems like hard disk drives, existing approaches to back-power electronics during a power loss event are inadequate due to reduced winding turns and smaller form factors, which can lead to insufficient power generation from motor kinetic energy.
Innovation Solution
A controller operates a brushless direct current (BLDC) motor as a boost regulator during supply-loss events, utilizing back electromotive force (BEMF) voltage to supply current to the load voltage node by controlling high and low side switch devices in a boost mode, thereby extending the operating time and enabling orderly shutdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If three phase alternating current back electromotive force (BEMF) voltages from the motor are rectified to supply power, then power can be generated from motor kinetic energy, but the power generated is insufficient for smaller motors with less winding turns
Solution Approach 1:
The patent changes the operational parameters of the motor by controlling the duty cycle of switch devices to operate in boost mode rather than traditional rectification mode. This parameter change allows smaller motors with fewer winding turns to generate sufficient power by utilizing the boost converter function to amplify the BEMF voltage.
Solution Approach 2:
The system dynamically switches between normal mode and boost mode based on power supply conditions. During supply-loss events, the controller dynamically adjusts the switching duty cycle to maximize power extraction from the motor's kinetic energy, enabling adaptive power generation that works effectively with smaller motors.
2Duration of action of moving object
If the motor is operated as a boost regulator during supply-loss events, then the load voltage can be sustained and operating time extended, but the device complexity increases due to additional control requirements
Solution Approach 1:
The existing switch devices in the motor driver circuit are made multi-functional by programming them to operate in boost mode during supply-loss events. The same hardware components perform both their normal motor driving function and their secondary function as boost converter switches, eliminating the need for additional dedicated backup power circuitry.
Solution Approach 2:
The motor itself serves dual purposes: it functions as both the motor during normal operation and as the energy source (through its BEMF) during supply-loss events. The controller leverages the motor's own kinetic energy and electrical characteristics to power the system during failures, making the system self-sufficient without external backup power sources.
3Reliability
If existing approaches are used with smaller form factor motors, then cost and size are reduced, but the ability to back-power electronics during supply loss becomes inadequate
Solution Approach 1:
The patent changes the operational parameters of the motor by controlling the duty cycle of switch devices to operate in boost mode rather than traditional rectification mode. This parameter change allows smaller motors with fewer winding turns to generate sufficient power by utilizing the boost converter function to amplify the BEMF voltage.
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 effectively sustains the load voltage and extends the operating time by converting motor kinetic energy into electrical power, ensuring a controlled shutdown even when the external power supply is lost, improving the reliability of smaller and lower-cost motor systems.
Implementation Method 1
utilize a back electromotive force (BEMF) voltage from the motor winding
Data Source
AI summary
A circuit includes a driver circuit having a high side switch device and a low side switch device coupled to a load voltage node and a motor winding output. A controller operates the high side switch device and the low side switch device. The controller operates in a normal mode to supply current to the motor winding output for driving a motor winding when an external power supply is available to supply the load voltage node. In response to detecting a loss of the external power supply, the controller operates the high side switch device and the low side switch device in a boost mode to utilize a back electromotive force (BEMF) voltage from the motor winding to supply current to the load voltage node.