Accessory Power Module Ripple Detection for MOSFET Protection
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Solution Overview
Problem
Accessory power modules in vehicles face damage due to voltage ripples exceeding the maximum voltage design level for power transistors, which can shorten their service life, especially when connected to high-voltage DC power systems with switching inverters.
Innovation Solution
A system with a peak detector and controller that dynamically monitors voltage ripples on the high-voltage bus, comparing them to a threshold voltage level based on the maximum rating of power MOSFET switches, and disables primary power switches when the voltage exceeds this threshold to prevent damage, using a peak detector circuit with an in-line forward-biased diode and RC time constant tailored to the frequency and magnitude of the ripple voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the accessory power module operates directly connected to the high-voltage bus without voltage monitoring, then the device complexity is reduced, but the power transistors are exposed to voltage ripples that exceed their maximum design level, reducing reliability
Solution Approach 1:
The peak detector circuit continuously monitors the high-voltage bus voltage before the accessory power module processes it, detecting voltage ripples in advance. When voltage exceeds the maximum design level, the controller preemptively disables the power transistors, preventing damage before it occurs. This preliminary detection and protection mechanism resolves the contradiction by adding minimal complexity to gain significant reliability improvement.
Solution Approach 2:
The patent introduces a peak detector circuit and controller as intermediary components between the high-voltage bus and the accessory power module. This intermediary system acts as a protective barrier, measuring voltage levels and controlling the operation of power transistors to prevent exposure to excessive voltage ripples, thereby improving reliability without requiring fundamental redesign of the power module architecture.
2Reliability
If heavy filtering is used to reduce voltage ripples, then the reliability of power transistors is improved, but the device complexity and cost increase due to additional filtering components
Solution Approach 1:
The patent replaces mechanical/passive filtering approaches with an active electronic control system. Instead of using heavy LC filters to physically attenuate voltage ripples, the system uses a peak detector and controller to actively monitor and switch off power transistors when voltage exceeds thresholds. This substitution achieves the same protective function with reduced component complexity and better adaptability to varying ripple conditions.
Solution Approach 2:
The system dynamically changes the operating state of power transistors based on detected voltage parameters. When the peak detector identifies voltage ripples exceeding the maximum design level, the controller changes the transistor state from conducting to blocked, effectively changing the electrical parameters of the power conversion process to avoid damage while maintaining normal operation during acceptable voltage conditions.
3Productivity
If the accessory power module continuously operates at maximum capacity, then the productivity is improved, but the power transistors are exposed to excessive voltage levels that reduce their service life
Solution Approach 1:
The patent implements a feedback control loop where the peak detector continuously monitors the high-voltage bus voltage and feeds this information to the controller. The controller uses this feedback to make real-time decisions about power transistor operation, disabling them when voltage ripples indicate potential damage and enabling them when conditions are safe. This feedback mechanism allows the system to maintain productivity while protecting components through dynamic, condition-based control.
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 solution effectively prevents exposure of power MOSFET switches to excessive voltage levels, extending their service life by directly measuring peak ripple and AC gain, thereby enhancing the reliability and longevity of the accessory power module.
Implementation Method 1
A peak detector is coupled to the high voltage input filter downstream from the high-voltage bus
Implementation Method 2
an RC time constant for the resistor and the capacitor is determined based upon the frequency and magnitude of the ripple voltage and a target recovery time
Implementation Method 3
An embodiment of the peak detector is an electrical circuit having an in-line forward-biased diode arranged upstream of a resistor and a capacitor
Data Source
AI summary
An accessory power system includes an accessory power module having primary power switches, a transformer, and secondary rectifiers. The primary power switches are electrically connected to the high-voltage bus, and the secondary rectifiers are electrically connected to the low-voltage bus. A peak detector is coupled to the high-voltage bus. A controller is in communication with the peak detector circuit, and operatively connected to the primary power switches. The controller dynamically monitors, via the peak detector circuit, a ripple voltage of the high-voltage bus, compares the monitored voltage with a maximum threshold voltage, and disables the plurality of primary power switches when the ripple voltage of the high-voltage bus is greater than the maximum threshold voltage, and reactivates the primary power switches when the ripple voltage of the high-voltage bus is less than the maximum threshold voltage.