Integrated Limiter and Active Filter for Automotive Remote Powering
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Solution Overview
Problem
Remote powering systems face challenges in current limiting, load dump protection, and high-frequency ripple filtering, particularly in automotive environments where voltage transients and varying DC output voltages with ripple can cause interference and damage.
Innovation Solution
An integrated arrangement using a single transistor, specifically a MOSFET, with three control circuits to limit current and voltage, and an active high-frequency filter, where the second control circuit generates a reference value based on input voltage to reduce power loss and provide load dump protection, and the third control circuit adjusts the reference value to minimize power loss across the transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple separate circuits are used for current limiting, load dump protection, and active filtering, then each function can be independently optimized, but the device complexity and cost increase
Solution Approach 1:
The patent combines current limiting, load dump protection, and active filtering functions into a single integrated circuit that shares common components such as the operational amplifier, reference voltage generator, and transistor. This merging reduces device complexity and cost while maintaining the reliability of each protection function through dedicated control paths within the integrated architecture.
Solution Approach 2:
The integrated circuit is designed to perform multiple functions simultaneously: current limiting through the first control circuit, load dump protection through the second control circuit, and active filtering through the third control circuit. Each control circuit can operate independently or in coordination, allowing the single device to provide comprehensive protection and filtering without requiring separate dedicated circuits for each function.
2Ease of manufacture
If a fixed reference voltage is used for load dump protection, then the circuit is simple to implement, but power loss increases and protection effectiveness decreases under varying input voltage conditions
Solution Approach 1:
The patent employs a dynamic reference voltage that varies with input voltage conditions rather than using a fixed reference. The reference voltage is generated through a voltage divider network that automatically adjusts based on the input voltage level, allowing the load dump protection threshold to adapt to changing operating conditions. This dynamic adjustment reduces power loss by avoiding excessive voltage clamping while maintaining effective protection.
Solution Approach 2:
The circuit incorporates feedback mechanisms where the output voltage and current are continuously monitored and fed back to the control circuits. This feedback allows the reference voltage and control parameters to be automatically adjusted based on actual operating conditions, optimizing the balance between protection effectiveness and power loss reduction without requiring complex external control systems.
3Device complexity
If high-frequency ripple is not filtered, then the circuit remains simple, but data interference occurs and DC/DC converter performance degrades
Solution Approach 1:
The patent introduces an active filtering stage that acts as an intermediary between the power input and the DC/DC converter. This filtering circuit, implemented through the third control circuit and associated components, selectively attenuates high-frequency ripple while passing the DC component, thereby preventing data interference and reducing the burden on the DC/DC converter without requiring complex passive filter networks.
Data Source
AI summary
An integrated limiter and active filter constituted of: an input node; an output node; a transistor coupled between the input node and the output node; a first control circuit coupled to the control terminal of the transistor and arranged to limit the amount of current flowing through the output node to a predetermined value which is responsive to a signal received at a first reference input; a second control circuit coupled to the control terminal of the transistor and arranged to limit the voltage appearing at the output node to a predetermined value which is responsive to a signal received at a second reference input; and a third control circuit coupled to input node and arranged to provide the second reference input, the third control circuit arranged to set the second reference input responsive to the input voltage and to a predetermined maximum allowed output voltage.