Vehicle Generator MOS Transistor Overheating Protection
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Solution Overview
Problem
Existing electric rotating machines for vehicles fail to effectively prevent MOS transistors in rectifier modules from overheating, particularly due to the inability to accurately detect temperature and manage parasitic diode heat in MOS transistors used in power generators.
Innovation Solution
An electric rotating machine design incorporating a field coil, armature coil, switching unit, switching control unit, generator control device, temperature detecting unit, and overheating protection unit, where the overheating protection unit sets one switching element to an on state and another to an off state to manage phase voltage and prevent overheating by controlling the supply of exciting current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switching element is turned off to reduce heat generated during conduction, then heat generation is reduced, but heat from the parasitic diode increases causing overheating
Solution Approach 1:
The patent changes the control parameter from simple on/off switching to phase-shifted PWM control. By adjusting the phase shift angle between gate signals for upper and lower arm switching elements, the system optimizes the conduction timing to minimize parasitic diode heat while maintaining efficient power conversion. This parameter adjustment resolves the contradiction by finding an optimal operating point where both conduction losses and parasitic diode losses are minimized.
Solution Approach 2:
The patent implements temperature detection feedback for each switching element and uses this information to dynamically adjust the control signals. When overheating is detected in a switching element, the system modifies the gate signal timing or duty cycle to reduce current through the parasitic diode. This feedback mechanism allows real-time resolution of the heat generation contradiction based on actual thermal conditions.
2Measurement precision
If temperature detection is implemented for each MOS transistor in the rectifier, then accurate temperature monitoring is achieved, but device complexity and wiring increase
Solution Approach 1:
The patent combines multiple temperature detection functions into a single integrated temperature detection unit that monitors all switching elements. Rather than implementing separate detection circuits for each MOS transistor, the unified unit shares common components and processing logic, achieving accurate individual temperature monitoring while minimizing device complexity and wiring requirements.
Solution Approach 2:
The temperature detection unit is designed with multi-functionality, serving both as a monitoring system and as a control input for the overheating protection mechanism. The same detection circuitry provides data for both thermal management and for triggering protective actions, eliminating the need for separate detection and control systems.
3Power
If conventional field current control is used based on field coil temperature, then generator output is controlled, but rectifier MOS transistor overheating cannot be prevented
Solution Approach 1:
The patent segments the control function into two independent parts: field current control for power management and switching element temperature control for protection. The overheating protection unit operates independently from the field current control, allowing each function to be optimized separately. This segmentation enables precise control of rectifier temperature without interfering with generator output management.
Solution Approach 2:
The patent introduces an intermediary overheating protection unit that acts as a mediator between the temperature detection unit and the switching element control. This intermediary receives temperature data, determines whether overheating is occurring, and triggers appropriate protective actions by modifying switching element gate signals. This intermediary layer protects the rectifier while allowing conventional field current control to continue managing generator output.
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
This design reliably protects MOS transistors from overheating without the need for additional connection lines, simplifying wiring and structure, and ensures efficient operation by accurately managing heat generation and detection.
Implementation Method 1
a field coil of a rotor, an armature coil of a stator forming a multi-phase coil... The field coil magnetizes field magnetic poles of the rotor in response to an exciting current flowing through the field coil and generates a rotating magnetic field from both the rotation of the rotor and the magnetized field magnetic poles, the armature coil generates an alternating current voltage induced by the rotating magnetic field
Implementation Method 2
The switching unit rectifies the alternating current voltage induced in the armature coil
Data Source
AI summary
A generator has a field coil of a rotor, an armature coil of a stator, a control device supplying an exciting current to the field coil when detecting rotation of the rotor, and a control circuit alternately setting an upper arm transistor and a lower arm transistor in on state in a rectifier module to generate a phase voltage. The control device detects the rotation from a periodic change in a sign of the difference between the phase voltage and a reference voltage. When the rectifier module is overheated, the control circuit sets the upper arm transistor in the off state and sets the lower arm transistor in the on state to almost fix the phase voltage, the control device detects no rotation and stops supplying the exciting current, and the rectifier module generates no phase voltage to decrease temperature of the rectifier module.