MOSFET Linear Mode Control for Electric Motor Noise Reduction
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Solution Overview
Problem
Electric motors in motor vehicles generate significant acoustic noise, particularly during starting phases and low-speed operations, due to the stator windings, which is undesirable for sound emissions.
Innovation Solution
A power supply system that reduces the DC voltage supplied to the electric motor during starting and low-speed operations by using a MOSFET transistor as a safety switch, controlled to operate in a linear mode, reducing the voltage value linearly with decreasing speed, thereby minimizing sound emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If full DC voltage is supplied to the power circuit during motor operation, then the motor receives sufficient power for normal operation, but acoustic noise emissions increase significantly during starting and low-speed phases
Solution Approach 1:
The patent applies the dynamics principle by transitioning the MOSFET safety switch from static operation (fully on or fully off) to dynamic operation (linear region). During starting and low-speed phases, the MOSFET operates in its linear region to dynamically reduce the voltage supplied to the power circuit, thereby reducing acoustic noise. During normal high-speed operation, the MOSFET switches to saturated mode to provide full power. This dynamic adjustment of the power supply voltage based on operating conditions resolves the contradiction between reducing noise and maintaining sufficient power.
Solution Approach 2:
The patent applies the parameter changes principle by modifying the voltage parameter supplied to the power circuit based on motor operating conditions. The control circuit monitors motor speed and adjusts the MOSFET's drain-source voltage accordingly. During starting and low-speed phases (when acoustic noise is problematic), the voltage is reduced by operating the MOSFET in its linear region. During normal operation, full voltage is restored. This parameter adjustment directly addresses the technical contradiction by changing the voltage level to match operational requirements and noise constraints.
2Loss of energy
If the MOSFET safety switch operates in saturated mode, then low resistance connection provides efficient power transmission, but voltage reduction capability is lost during noise-critical operating phases
Solution Approach 1:
The patent resolves this contradiction by making the MOSFET operation dynamic rather than static. The control circuit selectively switches the MOSFET between saturated mode (for efficient power transmission during normal operation) and linear region operation (for voltage reduction during starting and low-speed phases when noise is problematic). This dynamic switching allows the system to optimize for either efficiency or noise reduction depending on the operational context, eliminating the need to choose one mode permanently.
Solution Approach 2:
The patent applies periodic action through the control circuit's continuous monitoring of motor speed and periodic switching of the MOSFET operating mode. The control circuit regularly assesses whether the motor is in a noise-critical phase (starting or low-speed operation) and adjusts the MOSFET's operating region accordingly. This periodic evaluation and adjustment ensure that the system maintains optimal performance characteristics for the current operational phase while minimizing acoustic noise emissions.
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 reduces sound emissions from the electric motor by proportionally decreasing the power supply voltage during low-speed operations, addressing the noise issue associated with stator windings.
Implementation Method 1
a means for controlling the gate of the MOSFET transistor able to set said transistor in the closed position in a saturated operation mode for a set speed higher than said threshold speed, or in the closed position in a linear operation mode for a set speed less than said threshold speed
Data Source
AI summary
The invention relates to a power supply system of an electric motor (1) comprising a power circuit (3), the input terminals of which are connected to a DC voltage source, and an electronic circuit (4) for controlling the electric motor (1) based on a control signal representative of the set speed of the motor. According to the invention, the system comprises a means (6) capable of reducing the DC voltage value received by the power circuit (3) during the starting of the electric motor (1) and/or during operating phases in which the set speed of the electric motor (1) is below a threshold speed.